see if you can get video of it on a lift, taking the video forward to see if there’s a likely source for that - what looks like an old leak.
Does carfax / Oasis show anything about it?
And... TBF, the guy could have had a cheapskate neighbor like me, who refused to take their 20 quart diesel oil change to a recycle depot - any auto zone, etc will do - instead he through it in the trash and when the truck compacted their trash it left an Exxon Valdez level oil slick on the pavement in front of their place, which I drove right through not even seeing it. So there’s that possibility ;-)