The Mystery Stain

When something magically appears on the walls, sofas, floor or counters I generally know who put it there and what it is. But this stain has me mystified.

A yellow stain on the curve of my bathroom counter.  I think it was my 2 yr old, just because no one else is acting guilty.  And I don't know what it is.  I am guessing its candy.  Though I wouldn't know where he would have gotten yellow candy.  All the markers are in their place and up high.  All the paint is secured in its place. I don't think its crayon because it appears to be in the shape of a palm.   I even smelled it, and it has no smell.  And no, I am not licking it.  I have scrubbed and scrubbed and scrubbed yet a remnant still remains.  Which makes me think if it is candy what is it doing to our insides?!