As some of the above posters said, I think there is a sweet spot for results, 2008 seems to be that spot for me or so I’ve noticed. Anything before that may not be online. Another possibility is that the results were entered on Coolrunning.com. It was a huge online resource for not only road events but track events as well. Incredibly unfortunate that when they shut down the site they get rid of most of the results.
I feel fortunate to have run in the time where everything is online. I finished school in 2019, and other then a few meaningless duel meets, and 3 middle school results of mine that were deleted on coolrunning, every race I ran is pretty much online. All my PRs are also findable and online.
I can’t imagine what it was like before online archives to have to take people for their word about times they ran. Seems very frustrating, especially when you have no way to prove them wrong. I would’ve hated being a runner in the 90s.