Couple of questions. First, was there an attendant at the lounge when you were harassed (assume there was based on your comments)? If there was, did you report the harassment to the attendant? Did you get the name or room number of the other guest?
If you did not notify the attendant immediately (assuming there was one) and you did not get the name / room number of the other guest, there is not really too much that the hotel can do. If you give a description of the guest, the hotel can not just go up to a "suspected" person and ask if he was the person that offended you.