What is the ruling on someone who took a prayer beads (misbaha) from the university, does not know its owner, did not return it to its place, and is leaving the university? How can he absolve himself of responsibility for it?

If the rosary is ordinary and its owner does not seek it, then it is permissible to pick it up and benefit from it as long as its owner is unknown. This is the view of most scholars. However, if it is valuable and its owner is seeking it, then it is obligatory to announce it for a year. If this is not done without an excuse, then the one who picked it up has sinned. And if it is impossible to reach its owner now, then it must be given away in charity.