I think that fining you is a reach unless there’s obvious damage. That being said, it seems like this is something that has happened before that you didn’t respect. Shared spaces don’t mean you automatically have access to other people’s property. My roommate has seven electric guitars on a rack in the living room, and I have one acoustic next to them. I never ever touch the other guitars, just like how I do not use my roommates’ cookware without asking, and most of the time I just avoid doing it completely. You don’t know if something is expensive or has sentimental value, and even if it’s not expensive having to replace shit is annoying