The resolution of this issue will likely turn on a several key points:

1.  What exactly were you hired to do?

2.  Were you hired to provide an "opinion" on title (usually only attorneys are allowed to do that) or merely provide abstracting and/or recording services?

3.  Were you asked to and did you represent to the lender whose second mortgage it was that it constituted a valid second lien on the property?

4.  Even though the attached legal description may have been in error, was there other identifying information in the complete mortgage document by which the property could be identified (e.g., a property street address, tax parcel I.D. number, etc.)?  This is a state law issue, but in many states a "short-hand" description of the property may be sufficient to put a title searcher on notice that a mortgage lien may exist, and thus prompt further investigation.  Someone may have erroneously concluded the mortgage need not be paid because of an inadequate description, but until a court determines that its not sufficient, someone's opinion is not conclusive.

5.  This is not a "DIY" project.  If you have errors & omissions (malpractice insurance) you should (actually, you must) immediately notify your carrier of a potential claim (unless the amount claimed is so minor you feel you can pay it out of pocket).  They will have claims attorneys on staff who can look at the situation and determine your responsibility.    If you don't have E & O coverage (and perhaps even if you do), you should find a good real estate attorney who can look at the situation, review all documents and give you an opinion as to your liability.  If litigation ensues, you will need litigation counsel for sure.

Do not make any statements to the other side's insurance company, attorneys, representatives which may inadvertently imply liability.  (See # 5.)

Good luck, and don't assume you're automatically liable.