It can happen to lose something in the University. The Polytechnic has a number of offices responsible for collecting all the material found in the campus and return it to the owners, if by number, here you can find all the details: https://www.polimi.it/it/servizi-e-opportunita/altri-servizi-e-opportunita/oggetti-rinvenuti/. If I find something in the University take it to the concierge the nearest office or found objects.