Shannon,

If the mortgages are not way old, they may still show on the borrower's credit report with the lender's successor listed as the creditor.  If the successor is still in business, the credit report may even show a phone number.  If not, it may at least give you a more recent starting point to find the current servicer of Washington Square's portfolio, if any.  It can be a big time waster trying to track some of this stuff down, but you can get lucky at times and get a release. 

If the loan you are insuring is brokered, ask the broker to have a look at the credit report to see if the loans are still showing up.

Otherwise, you might try The Lane Guide, which claims to have information  on over 140,000 open and closed banks, finance companies, mortgage companies and credit unions on a CD.  I have not seen the product, so cannot vouch for it.  But if you want to give it a look, the number is 1-800-526-3484.  Good luck.