Keep visiting each hotel every day and see if there is a backpacker in the first room at the top of the stairs. If there is talk to him. Repeat this on 4 different days, and you should get the souvenir.
There is a backpacker who moves around to a different hotel everyday. You need to talk to him several days in a row(I think 4) and he will eventually give you the Strange Souvenir. But it could be in any hotel.