Oil sitting on top of coolant “overflow tank”

Hey boys, I’m selling my 2001 double cab and someone drove about 2.5 hours to get here and we ran into the same problem, never heard of this before but then again I do home loans, I’m not a mechanic lol. My mechanic literally thought the potential buyer poured oil in the reservoir if they went on a test drive without me, to talk me into giving a discount for a blown head gasket. Would’ve loved to hear what the guy found out, if anything. I uploaded some pics, it’s the same thing right?

 

Unless I am mistaken (known to happen with alarming regularity), that pic is of your oil cap, not your coolant reservoir. You should have oil there! The cream colored residue is normal until the engine gets really warm. A few months after buying my truck, I went for a short drive and then checked mine (don't remember why). It was cold out and looked like someone had stuck a quarter stick of butter there. I freaked out, thinking the same as you. Turns out, thankfully, to be perfectly normal...

 

The only thing close between the original post and your's is that they are both under the hood.

And you might consider a new 'mechanic'.