How can a find a photo that I downloaded in 2020

Sure, that is possible. I have a license history going back to 2018. Check this link: https://stock.adobe.com/Dashboard/LicenseHistory

It will get you to the license history deshboard, where you can check the assets and the licensing date. As the history is sorted by date, you can easily find the date in question.

It would be easy if you happened to have the original asset number. Older assets, I believe, get pushed further back in the search queue unless they're sold multiple times. If you can think of some unique keywords that might have been used, I'd start the search from the end of the results rather than the beginning. And while unlikely, there's no guarantee it still exists if the contributor cancelled their account.