Now, the question is:
What happens if the manufacturer repairs the replaced frame and re-issues it?
What happens if the manufacturer doesn't repair the replaced frame and it is "lost" by the manufacturer, reassembled into a new firearms and used in a crime, then traced back to the original owner?
Personally, I would contact Glock and request that at least a portion of the frame containing the serial number be returned such that I can be assured that the serial number that is attached to my name in the MA database can not be used in a crime and traced back to me. OR a letter specifically stating the the replaced frame was destroyed and replaced with the new frame such that if any of the above occur, I have documentation to cover myself.
Even in New Hampshire where there shouldn't be a record that attaches me to that firearm, I would want the records to cover myself in the event that it comes back to haunt me.
I am aware of at least 1 select fire M-16 rifle that was reported as "lost" in Vietnam, reported as recovered in a raid in NYC, reported as destroyed by the NYPD, then confiscated by a New Hampshire police department and the lower reciever was then turned over to the BATFE in exchange for an AR-15 lower reciever. After the BATFE received it, I can not verify what happen to it.