2, empty echo, it is hard to say, it may be in the corridor or bathroom, the hotel should not have such a big echo.
There are so many suspicious places that you are afraid that he won't admit the debt. Then you have to convince him to take it orally and dispel the misunderstanding-follow up and find evidence! Anyway, it's not far from work, even if you follow him, you won't lose anything.
4, there are many female colleagues in foot bath, and a girl may be afraid in the middle of the night, and the possibility of going home together is not ruled out. Before tracking, you should think of a way out. In case of being met, pretend to pick him up, or be jealous or heartbroken. . Different choices will lead to different results, so be careful.
Look at your performance in a crisis, I believe you can handle this matter!