If you have friends house sit/pet sit do you expect that they'll go through your things?

Honestly most people I know are bathroom lookie loos and will go through your medicine cabinet and such but not anything else.

I had two friends watch my snakes and other animals while Ryan and I were in Indiana. Yesterday when I returned to work I realized I'd forgotten my work keys and wasn't sure what I'd done with them and made a comment about it, well, one of my house sitting friends popped up and said she'd seen them in the drawer to my entrance way dresser (it has papers, books, and odds and ends in it). While I didn't say anything at the time this didn't sit well with me. And while she could have had an honest reason for getting in it I don't know and she didn't tell.
I had bills out too, now I wonder if they were going through my bills...then again I'm a paranoid person by nature.
In any case, would you say something or ask about as a way of finding out what they did go through or would you just sit back and make sure not to have them house sit again OR, just ignore it?