Based on your comment identifying the details in your email not referring to bag drop – but instead to boarding, I would tend to think you will be out of luck.
Generally, whatever you can get at the terminal is what you will get – successfully getting something out of an airline after the fact is a real challenge. In the future I would try and get in front of a person – and ask them to help you solve your problem. I generally in such a situation tend to admit to having made a mistake, but would really appreciate the help to resolve it without it costing me an arm & a leg (or firstborn child, or whatever other idiom you like and seems appropriate. the key is to help the person on the other side of the counter know you appreciate their work, value them as a fellow traveler in the journey of life and that you personally are simply a human who made a mistake)
It does sound like you did get a bit of the short end of a stick – I have missed plenty of flights and always been re-scheduled without being charged, even for a difference in fare. EXCEPT for one notable occasion when I had to change an easyjet flight from Europe to the UK. On that occasion, we had 2 seats, and had to pay a very steep price I think it was over £100 each.
Note To All: NEVER try to change an easyjet ticket after purchase!
Having said all that, you are talking about a flight on United – arguably one of the most hated airlines in the US. This is the airline that dragged a seated passenger off with a security guard, all so they could seat a staff person being shifted around the country:
United boots passenger
It is in fact because passengers frequently miss flights that airlines overbook!
I don’t like your chances of getting much out of them. Give it a go certainly – but be prepared for quite the run around, very little sympathy and a potentially unpleasant experience. Not quite as bad as that guy – but maybe not so great.
Credit:stackoverflow.com‘