I moved into a new apartment and the old roommate left things, she said whatever is left is trash, she does not want, is from former roommates or the landlord. I threw away things, gave away things. I also used some worn shoes and old blankets, etc But I also found a nice suit, etc. It made me pause- can I use these nicer clothing items? Are the hefker? How do I go about finding the owners? Are they disregarded like the previous items? Because of their value it made me pause and write to you. The unit has been rented for +3 years. The landlord and renters are Jewish.
On the assumption that you didn’t find the clothing in a hidden place that cold have been overlooked when the roomates moved out, what was left from the former roommates, they would already have known about it and don’t want it. However if it is the landlords, that he left in his apartment it would belong to him. I would advise you to say something to him, and after he says that he doesn’t want anything that he might have left in the apartment, you can use it all.
CH:M 260-3, Shach ibid 11 Nesivos Hamishpat ibid 7, Hashovas Aveida Khilchoso 8-1, Poskim.