1. The guy doesn't seem like a computer expert. Don't dismiss his speculation merely because he's unable to explain what he observed as an engineer or programmer would.
2. There are always lots of more reasonable explanations for any suspicious activity than spying. This will be true for almost every case of actual spying that isn't unambiguously discovered.
4. The fact that one possibility is more likely does not disprove the possibility that it was the other. Do you really believe that every gov't agent is above a juvenile prank, or that none are buffoons? Or perhaps it wasn't a gov't agent but some other person.
5. Hotel safes are universally crappy and usually have a default master password that is known to criminals, and spies. I'll assume there are other ways to break into them as well.