Oh boy. To me, that is worrisome. The arms around him, the faces close. The alcohol. The you not being there.

I used to travel internationally for a living. All over the place. And what I know about cheating on business trips (not from my own experience, but from watching it happen around me) is that these things often just happen sort of in an instant. There's touching and arms and cheeks and drinks and then, suddenly, somebody plants a big, wet one on the other party. And then it's off to the room. The end.

The key to preventing this sort of thing is not putting yourself in 'harm's' way. That means, if you're a guy and you're straight, don't be alone with a potential hookup. Don't drink alone with a potential hookup. It's dangerous. Stuff happens. And once it does, you can never get it back. Respect you primary relationship/partnership/marriage. Respect your partner enough not to want to even have the appearance of something questionable going on.

In my opinion, your partner should know enough to know this stuff. Personally, I think you should have a chat with him about it. If he doesn't see any of this as a potential problem, then maybe that tells you something you need to know. I wish you all the best!!