When you took delivery of the car, did you ask about a build sheet? When the cars were new- a build sheet wasn't important. So if it got pitched, who threw a fit? It's only in the last few years that build sheets have gained such notoriety.
No, I didn't ask about it when I took delivery, but then on the other hand I was slack-jawed at finally having my own brand-new TA. The salesman even did the obligatory walk-thru of all the "features", none of which registered on me because I was in awe of the new car smell and the bold dark blue color. My first return to reality was when I realized, as I pulled off the dealer's lot, that the gas tank had less than 1/4 in it and I had 30 miles to drive to get it home. Unleaded fuel was new in those days and not every station had it yet.
But I was aware of what the build sheet was, as I had them for earlier cars I'd driven. I have the one for my 66 Chevy Impala somewhere. Although I didn't know what all the codes were I realized it was an important part of the car's history, and I figured I'd find it someplace when I got around to looking for it. I even managed to save most of the original new car sticker from the passenger's window when I removed it, which was shortly after I got the car because it was tough to drive with that covering up a good part of your viewing angle from that side.
The closest I have to my own build sheet is a copy of my buddy's build sheet. His car was ordered at the same time as my car, but from a dealership in Illinois instead of Indianapolis. The cars were identical except that his car was silver/black with the charcoal hood bird and he had an AM/FM stereo in his, whereas my was a "no bird on the hood" car and a radio delete. Otherwise, they were identical -- deluxe interior, rear window defogger, AC, Rally II wheels with full-size spare tire. He found his build sheet under the rear seat cushion -- it wasn't even wrinkled.