The best news is that you don't need a lawyer to file the papers and ask for a stay. The Consumer Warning Network offers a form to download if your lender has already filed suit. Fill out the first form and send it to your lender by certified mail. Call the Clerk of the Court in your area to find out if you also need to send copies to the court and to the attorneys for the lender.
If the lender has not yet filed suit, use the second form, which is a customizable letter to your letter asking the lender to produce the note. If you don't get a response and the lender files a foreclosure lawsuit, use the first form and then follow up with the step below.
Your lender has thirty days to respond, and then you can file a motion to compel, asking a judge to make them produce the note. The judge does not have to decide in your favor, but he might. He can also choose to accept an affidavit from the company that admits the paperwork is lost.