In addition, I'm fairly sure the ATF could search a given address that you have to locate the current licensee or previous licensee for that particular address, and go from there. The dealer number is not necessary per the required documentation in your bound book.
I think my C&R firearms number upwards of 50. Non are recorded in my bound book with an FFL number. Only the name, and address of the distributor I bought them from. A dealer FFL is only required on the disposition side of the bound book. That is if you sold the gun to a dealer. If sold to a non-dealer name, and DL or other identifying number is required.