I knew the dealer that originally sold my car (due to the plaque affixed, and the tag frame). Sometime after I purchased the car in '76 (it might have been as late as 1980 or so), I went by the dealership and asked if anyone had worked there in '69.. There were a couple of salemen, etc who had been there when the dealership opened in '68. When I explained and described my car (I was not driving it - although that might have triggered some memories and maybe got some help), they told me the old records had been stored and then destroyed...
Forward 30 yrs... Last weekend we had a large car show in an adjacent town, and I ran into an old friend who had been in the Chevrolet parts business for many years since the late '70's or early 80's.. He now works at that dealership (Joe V Clayton Chevrolet in Arab, AL). After the car show, I gave his daughter a ride in my ZR1 and he and his wife followed me home in their truck (48 Chevy rat rod but nice).. When he saw my Camaro, his wife commented.. look it was sold at Joe V... and he said. I wish I'd known you had that car a couple of years ago, before they tossed all the old records (He told me they had those records in the attic, but they only tossed them 2 or 3 years ago!~)..
Basically this story is intended just to point out that even if they have the records, they don't want to spend the time/effort to go thru them to find YOUR sales paperwork.. (I had even offered to pay them for the time way back when.. and offered to come and help.. but no dice!..)