Geez, you'd think they could've washed it first. https://www.mecum.com/lots/CA0819-3...111778773&mc_cid=b2457b91d8&mc_eid=d28948613a
Maybe, he was afraid of washing off Elvis's peanut butter stained fingerprints. There's probably crumbs from one of his sandwiches lost in between the back seat cheeks. In any case, more proof needed
After this amount of time, either the mice ate the crumbs, or insects did. Any left over are likely fossils now.