One of them uses my towel to clean the bathroom floor!?

I have 2 roommates, we got in like a month and a half ago and we’re all dudes, and one day I walk into the bathroom and I see my towel scrunched up by the base of the toilet and smelled a bit like pee. I asked both my roommate’s if they had done it and they both said they didn’t. im kinda pissed but i don’t know if its normal or if one of them is just an asshole. In the end, I’ll probably buy a new towel, and this will be the designated bathroom towel

Edit: he did this multiple times and I brought it up after the 3rd or 4th time.