score:2
One aspect that most folks don't realize is that agencies like booking.com have a room block at the hotels they offer, that is they have four rooms booked for every day of the year (the amount varies depending on the hotel). When you book, they assign you one of these rooms. When these rooms are gone, they mark the hotel as sold out on their website. At a contracted time before the guests arrive they send booking details to the hotel.
They don't call the hotel each time someone books and they usually don't get additional rooms once their block is full. So a hotel could well still have rooms open even though booking.com's allotment is sold out. Conversely a hotel's website could show sold out while booking.com still has rooms available in their block.
Hotel ratings vary from country to country, so one country's 4 star might not be the same as another's. Some countries assign ranking by an organization, some countries have self ranking, some countries simply make things up. Agencies like booking.com depend a great deal on honesty from hotels with the properties descriptions, with many thousand properties it is not always possible to personally inspect each one.
What recourse do you have? Best is to honestly review the hotels on booking.com and TripAdvisor, skip the fraud accusations and stick with property details. Send booking.com an email or postal letter outlining your situation and ask what they can do, leave out the emotional tirade and accusations, concentrate on the facts.
btw: having used the bathroom is the primary reason around the world for not refunding room charges after you have been in the room as there is really no way to prove or disprove you used the toilet while in there, thus requiring the room to be cleaned.
Upvote:4
As you have edited your question, I edit my answer, I will come back to it later to fill out the details.
With all online purchages, whether items or services, it is up to the buyer to double check that what is on offer is what they require.
With hotel bookings you do that by checking reviews on several sites, including having a good look around on the website of the hotel if they have one.
If those reviews as well as the description do not agree with what you find, you complain to the owner and/or front desk staff so they can adjust or offer compensation. Only when that fails you consider other steps, walking away is just the last option.
Do not forget that star ratings are different between different countries and sometimes even different chains of hotels within a country and that your expectations may have been off for this hotel.