See if a WARC has been saved already: take the URL+\n and see if that text exists as a raw IPFS block (not the best solution). And just because a WARC of a URL is saved to multiple computers, doesn't mean that that webpage was correctly captured. For example: Invidious error page at /watch?v=id where sometimes that webpage loads with no error (also use &nojs=1 to save comments in the warc).
I was thinking: is there a way to extract files/urls from a WARC in mobile? But this question doesn't matter so much to me now as I can get wget's raws and like look at the corresponding CDX for metadata.