The auctioneers have your title, so you don't know who bought your car unless you recognize them or they come up and introduce themselves.

My dad sold his car at auction and never found out who bought it.  Technically, he knows the name of the person who was bidding, but they were acting as an agent for somebody else.  Supposedly the car went to a private museum/collection in California, but we never found out where.  And my dad had a bunch of valuable and rare parts that went with the car and they were supposed to send for them.  My dad figured he'd find out then, but they never collected the parts.  So we still don't know who bought the car.