When the buyer calls in to complete the transfer, the CFC will ask them their town/city of birth. That's one of their trip up checks. If the person can't answer, the transfer won't go forward, and will no doubt be flagged for investigation of some type. You need to wait for a mail notification that the transfer has been completed. You can then send them their firearm.
As far as insurance goes.....it isn't worth a ball of spit if the sender can't prove how much the item was valued at. In your case, you would need to provide an original sales receipt for the gun. If you don't have that, you're going to have one hell of a fight on your hands. Of course, they never seem to mention that. I can only think of once that I've bought shipping insurance from Canada Post, and it wasn't for a gun.
If a restricted firearm doesn't show up, and CP is just giving you the "too bad so sad" routine, start asking for names and addresses and inform them what was in the package. Tell them you need the information for when you call into the RCMP to report it, and that they will no doubt be investigating what happened to the package. It's kind of amazing how things mysteriously turn up when the cops get involved with their internal BS.