~~The very old task T23345 got implemented~~ Sorry, mixed up old versions of a not deleted file ( https://www.mediawiki.org/wiki/Manual:Oldimage_table ) and deleted images ( https://www.mediawiki.org/wiki/Manual:Filearchive_table ).
We can now search the filearchive in the api by hash, see https://commons.wikimedia.org/w/api.php?action=query&list=filearchive&faprop=sha1&fasha1=c0f895d6a4973ef711d9749fb9b83ce65ac0c53f . That means we can finally add the site function to access this in pywikibot. Function in API is described at https://www.mediawiki.org/wiki/API:Filearchive and https://commons.wikimedia.org/w/api.php?action=help&recursivesubmodules=1#query+filearchive . Implementation could be done the same way as the allimages, see https://github.com/wikimedia/pywikibot/blob/master/pywikibot/site.py#L4434