Same thing happened to me in the Sheraton, Warsaw. Unfortunately for the poor chap who walked into my room, I dont take kindly to being awoken by strangers and he left with a few choice words following him into the corridor.
Stopped by the front desk and let them know the next day, didnt ask for compensation, and recieved a sincere apology. The next time I stayed there however I walked in on the biggest 4 room suite I have ever seen ^