You can skip trace them, or just man up and knock on the door!

Never are YOU responsible personally for leins on a property if you win it at auction. The liens that might encumber the property are on the property, not you. Now if you own the property after the auction the lien holders can technically depeding on the state and type of lien foreclose on the property to get payment for the judgment amount they are owed.

If it's a foreclosure not a tax lien and the lien that foreclosed and you won the property from is a junior lien, like a HOA/condo ...