Property back on market - lien issue?

[Sweta Govani]

I am considering putting in an offer on a property that recently got back on the market. The seller's agent said: "reason for back on market is unknown lien was found on property and previous buyer didn't wait to be figured out, ready to move forward now". 

1) I'm a complete newbie so this makes me very nervous. Can you please explain what this might mean? 

2) What is the best way for me to get to the bottom of this? I am most likely going to have to do it during the option period so want to make sure it will be quick and 100% confidence.

3) What else should I be thinking about / doing?