Whenever you have someone house or apartment sit, just take it as fact that they're going to go through your stuff. Thinking otherwise is stupid of anyone. It's going to happen. If you don't want things to be seen or found, hide them better or don't have that parson there. I apartment sat for my hot older sister years ago, and admit..Pretty much the first visit, after doing what I had to do there, went through her drawers. Found some nude photos (a folder full) and took a few for myself. When she returned home and made me dinner as a thank you, she joked about it, saying didn't even have to look, just knew I found the folder and hoped I enjoyed the ones I took for myself. Wasn't mad at all. Found it funny. Understood that I, or anyone else, would go through her stuff.
Why is this gross? Concerning maybe, but not gross.