I wonder if there's something in it being a small guest house as opposed to a hotel. I use to stay in one for work reasons - called a hotel, in reality a large house converted with about 10-12 guest rooms. The manager was the son of the owner, and ran it on his own whims of the day. If you were in favour it really was home from home, and great for such a long stay welcome. But, if you dropped out of favour you pretty much had to leave. I would totally see this type of thing happening there.
This was my thought too. Fawlty Towers was, of course, based on a real-life guest house. There are people who are that fickle. The story is incomplete because we have no description of the ongoing situation, whether DH was given any money back that he’d prepaid and whether he returned to be kicked out and still wasn’t able to speak to the manager who originally gave permission.
For me it sounds perfectly possible that this has happened because a rogue member of staff has been given free rein in the absence of the owner/manager and has abused the power.
OP, of course the hotel can enter and move anything, so long as they don’t steal it. Your DH is staying temporarily on their property and there might be all kinds of reasons why they might need to move guests’ property, so they will retain the right to do so in all cases.
Sounds like your DH took the easy path and moved somewhere else without chasing this up. Is part of the frustration actually caused by the fact that he doesn’t stand up for himself and doesn’t make a fuss when he perhaps ought to? If this happened to me, I might well move as I couldn’t be bothered arguing with someone so obviously unreasonable, however I would certainly make a complaint about it, probably initially in private, then publically if that didn’t work. I’d want to try to ensure this chancer didn’t do something similar to someone else, with potentially a much worse outcome if there was nowhere else available at short notice.