Find a way to contact the domain owner. Lots of times, when a
webmaster purchases a domain, they must fill out certain details,
such as their name, email, and address. These are usually kept
under privacy, but there are usually ways to ask for permission to
contact the owner. You can reach some of these details - So long
they aren't under privacy - with many domain searching websites
(You can find one on google). And even if they are under privacy,
the domain search should be accompanied with details on contacting
the hosting service or domain service that is providing the domain.
Contact the owner or the domain hosting provider, and ask about a
domain transfer.