In a lien sale it is where the owner has a loan of some sort or has used the item for collateral, this is also known as a repo sale. The person has failed to pay and the property used for collateral has been taken for payment. The lien holder then sells the item for what ever money they can get, once sold the lien holder has to go back to court and get the difference between what the item sold for and the amount owed them.
In a repo/lien sale a title is not required, the lien holder must and would have court documentation showing that he has taken the property to settle the debt, then the lien holder with that court order and a notorized bill of sale to the buyer can obtain a new title for you as the purchaser.
I have done many of these in the past. Now you see these all go to auction now where it is all handled through the auction company.
Contact your local DMV and they will tell you what paperwork needs to be done and how.