[@Background Pony \#52BA](/forums/tagging/topics/general-tag-discussion?post_id=5341451#post_5341451)
Hmm, hard to say. I'd probably either tag it with something like "suspected artist:xxxx" or "artist:xxxx" + "artist needed". Plus I'd definitely explain the situation in the comments.
EDIT: Actually, instead of "artist:xxxx" + "artist needed", it would be better to use something like "artist:xxxx" + "artist guessed" or "artist uncertain". And of course still add a note in the comments.