When during meditation we forget where we are

This feeling isn't unexpected. But to ask if it's expected... one of the meditative points is to overcome the need to have expectations.

If we expect something to happen and it doesn't, then we're more or less causing suffering to ourselves; if we expect something to not happen and it happens, then we're causing the same kind of suffering: conflict and stress from that conflict which arises from dramatising the lack of control we have over the world. It's not unexpected for strange reactions to occur with any form of meditation.

It could be that your focus has gone so deeply on one thing that you're no longer focusing on your "where" but instead are looking at your "what" and the interconnections between mind and heart. Re-check the discipline you're being taught, and manage the situation by reconfirming that you aren't making any obvious mistakes. But once you've done that, it's not necessarily a mistake; it's likely just a reaction from ahaṃkāra (ego). Over time and with practice, it should diminish.

As to whether or not this is a mistake in practice, I think this classifies as "overthinking the situation". Accept that it happens, and it's a part of your experience. Eventually, you may even get into a state of non-locality, which would be excellent. While I wouldn't consider this non-locality, it certainly points to that as a possibility for future practice. But you can't make it happen; it just has to grow into that.

My answer would then be: Let go of your worry. It isn't serving you well.

Our perception of context is a compound phenomena (sankhara) fabricated or assembled (sankharonti) by the mind from multiple individual thoughts: what is this, where is this, what am I doing, what is my goal, where I came from, etc. As you can see thanks to meditation, mind does quite a lot of work to assemble what it calls reality.

This works the same way in the waking state as in a dream, except the waking state gives you more clues, but the effort of fabrication is the same.

This insight, that reality is a fabrication we make, is almost more important than meditation itself. It gives us new frame of reference in which we can finally choose how we perceive reality, by choosing what we turn our attention to ("guarding the doors") and gluing it together with power of will (loosely: faith, determination, mindfulness, concentration). So we no longer have to get stuck in negative thinking of the six kama-dhatu worlds. Instead, we can feed our mind with positive information, until it gets strong and healthy (first 3 jhanas). Once our will gets strong we can be free to choose our reality on case-by-case basis (4th jhana and beyond).

You say "awareness is an important concept in buddhism" -- but what is this "awareness" really? Aren't we always aware of something, even when we are obsessed with desire or negativity? In Buddhism, mindfulness (sati/smrti) is not just passive awareness of whatever worldly activity we may be performing at the moment, it is a mastery over one's context. We can see this power developing through five levels (panca bala): faith, effort, mindfulness, concentration, and wisdom.

1. At entry level mindfulness starts as faith in the live tradition. Inspired by an encounter with Sat-Dharma, your mind gets the bug of Buddha-fever. Unable to resist the urge to find out more, you keep thinking about mysterious Dharma.
2. At beginner's stage mindfulness means applying effort to constantly check one's current physical, verbal, and mental activity against the context of Eightfold Path. Is my mind presently biased by attachment? Is my current action motivated by egoistic intent?
3. The next level is when staying always mindful of the context of Dharma becomes automatic and no longer requires effort, which means one is now always operating in the phenomenological context of the Four Right Efforts.
4. At middling level mindfulness grows into concentration (samadhi) which means we can now design, assemble, and maintain any context we choose.
5. Finally, at advanced level mindfulness becomes wisdom (prajna), which means seeing all contexts at the same time and freely juggling their elements as required by a situation at hand.

Since the one who keeps track of where we are in time and space, the question really is asking what happens if I forget myself.

Here is how Dogen answers this question http://zmm.mro.org/teachings/meditation-instructions/

The great Master Dogen said, “To study the Buddha Way is to study the self, to study the self is to forget the self, and to forget the self is to be enlightened by the ten thousand things.”

In another text, Dogen mentions forgetting objects of thought. What is the place we think we are in but an object of thought. If we lose our memory through amnesia, the place we are in is not an objective place but a subjective memory experience that can disappear so that we cannot use it as a point of reference.

http://www.thezensite.com/ZenBookReviews/DogenManualofZen.htm

Dogen's second version of the Zazen gi expresses this scheme far more clearly. Bielefeldt's sixth chapter studies the vulgate text of the Zazen gi, noting Dogen's unmistakable departure from Tsung-tse's meditative framework centered on the mental exercise of "forgetting objects" of thought. In contrast to "forgetting objects," Bielefeldt points to "nonthinking" (hishiryo) as the key to Dogen's understanding of true meditation. There, the practitioner, instead of attempting to forget objects, becomes the state of nonthinking itself.

So if you are becoming the state of non thinking itself, then your experience is drawing from a deep well.

It may be unnecessary to mention that even if you find you are drinking from this deep well, you must forget that too. Even a greater impediment to our unfoldment and awakening than the attachment to places is the attachment to the idea we are attaining spiritual levels, or we have ATTAINED nirvana. Ditch this kind of thinking as soon as possible. Beginner's mind is every moment is fresh and unattached to the past, good or bad. So whatever you decide, let it go so you can drink deeper in the well of experience.

It is the matter of concentration. Whenever thinking of "where am I" arise, try to focus on meditation with what you start. If you start noticing breathing in and out at the tip of nose , just start it again. But it is not meant that you are not making progress. Mind used to get wander like that. All the things whatever happen , just focus simply on the meditation with what you start. It is better noting mindfully "breathing in, know it, breathing out , know it". Whenever you noticed wandering thoughts, just focus again on this "breathing in, know it, breathing out , know it".