Had my wallet stolen, and lost my airman certs as well as my medical cert. I called the FAA at 405-954-3261, and told them that I needed a fax of my certs (airman & medical). They faxed it within the hour, and that fax is good for 60 days. It's a simple piece of paper - just has your name, cert number, ratings, class of medical, etc.
In the meantime, you can go here and get the address to send the $2 and have them send you a replacement copy of your medical.