One of the most challenging things about living with roommates is remembering what belongs to whom. I was the first person to move out of my college apartment, and I accidentally left so many things behind. Luckily, my roommate was nice enough to take my forgotten stuff back to her childhood home so I could pick it up, but most roommates would not be so generous. I wouldn’t put it past her to throw my forgotten chess pieces in the trash. 

I’d say it’s more common for a roommate who’s moving out to forget things behind than to take things that don’t belong to them in the moving process, but you’d be surprised! Some roommates will take their roommates’ possessions on the way out and hope that nobody notices. Sometimes this is done unintentionally, misremembering what is theirs, but in the case of these roommates, the stealing was extremely deliberate.