Yes, I lost some of those too when I did mine years ago. On my 91 the gaskets were a clear film, very thin. Just used a very thin coat of hi-temp copper RTV on each side of the flapper for the ones that I lost. Worked well with no problems. In a later post with a pic of my dog, I saw where one of the gaskets went - on the floor. The little bastid probably stole it to play with it. :D
Maybe the mutt ran outta smokes and was pissed at ya for not rushing to get more.