It happens. Usually due to an error or delay in the check in process where the guest doesn’t end up showing as being in that room, and staff are convinced the room is empty. Hotel staff tend to be very set in their beliefs on these sorts of things, haha. Hence the lack of advance calling / knocking and the opening of latches. Obviously should not happen. Should yield an apology and some comp, but usually is simply a dumb error poorly handled, not anything nefarious.