Should I be worried/weirded out?

My boyfriend of nearly 5 months went out with work people on Wednesday. He ended up staying at some girl's house- she goes to a uni near his uni).I'm pretty confident that nothing happened between them, and I trust him explicitly (he's been on the receiving side of cheating in the past so I doubt he would do it to me) but apparently when he told his friends that he'd told me, they were shocked I hadn't reacted differently, angry or weirded out. He said himself that if I'd ended up sleeping in some other guy's bed because I was too drunk (as he was) then he'd be a bit weirded out. Am I weird for not reacting differently? Idk, I just feel like it is weird to be as okay with it as I am. Thoughts?