The title company will start by taking a statement of Identity from the seller and will verify the sellers claims first. This should be happening on the seller side as we speak. If there is a judgement then the seller can go to the claimant and get a waiver from them to release the lein. This also is administrative and may happen relatively quickly. I don't see why this would be a big issue since the you said it was a short sale and lender will receive any and all proceeds, there is no real benefit to the leinholder.
After all this has happened, if you like the home, you can still close so do see a lawyer, right away for a consultation. They can advise (in my estimation to your benefit) you as to how short circuit a foreclosure and the leinholders claim. You should, though, ask yourself if you want to invest the time and additional effort though.