I'm guessing from your post that it was gone before archive.org could crawl it? You can force archive.org to save specific sites immediately so that you can use their (permanent) link as a future-proof citation [0].

Alternatively, something like WebSatchel [1]. I have no experience with it, so can't tell you if it's any good, or whether there's other software that does a similar thing.

[0] https://help.archive.org/hc/en-us/articles/360001513491-Save...

[1] https://websatchel.com/a1/#/