I hate to be a pessimist but it's gonna be damn near impossible. It's like knowing a band 由 a few promo pics as opposed to songs and band name (trust me I speak from experience).
I'd say your best bet is to try googling a 评论 they left? If 你 remember any of them. It would probably have to be word for word though. 或者 if they were on an unpopular club 你 can go there and try to find them. Other than that I don't really know of a way.
你 can't A person's ign is their calling card if 你 can't figure that out. 你 can't figure out which 用户名 your friend has. It's like going into a neighborhood and forgetting what address your friend has. No identification no pinpoint shot to finding 说 friend..
