A situation we deal with a lot in the shop is people that have lost or misplaced their person identification number (PIN) that came with their License To Carry or Firearms Identification card. In July of 2013, gun shops can no longer process fingerprint information to verify a person's identity. As such, all firearm purchases need to be accompanied by the PIN that was provided with your LTC or FID cards. Many people have lost that information.
This is fairly common and nothing to panic over. The solution is to call the Massachusetts Firearms Records Bureau (FRB). When you call the FRB, they can provide your PIN over the phone once the take a couple pieces of identifying information.
Two pieces of information to have at-hand when you call them.
They will likely ask you additional information, but these two items are likely not things you will have memorized.
Once you gather these pieces, you can call the Firearms Record Bureau at (617) 660-4782.