My old '70 Challenger R/T 440 Magnum 4 spd super trak pak FY1 car didn't have a fender tag or build sheet either. When I put it up for sale, it went pretty quickly. All #s matched, just missing tag and sheet. Some people still want them even without all the documentation. Wish I kept that one.
Was the car restored or sold in original condition ?? Either way it must have been priced right ???
New owner will do what you didn't do and Northeast Mopar wants to do, have a tag made ...