Hmm... I didn't mention the grease to her until after the first incident. It's possible she could have put it on the floor I guess, but that seems... very not like her.
As far as what kind the grease is - it's very very black, on the verge of looking powdery without. I don't think this picture is actually grease (who knows though, maybe eyeliner IS grease, I don't keep up on this stuff) but this picture is what I'm dealing with:
Thats actually a good deal heavier than what was on my face, thankfully, heh.
I'm wondering if the source couldn't be something outside... I think it might be on the face since I get home from work, and it may just take her a little while to notice? It's possible. MY memory of order of events is always pretty terrible, though. Still, that does give opportunities - subway, bike ride home, although I really don't see myself pressing my face up against greasy stuff on any part of the journey. Hmm...
And the floor smudge is really the most confusing bit. If it was, like, in front of the door or something that might make some more sense - maybe I tracked it in from outside? Forgetting my keys/phone/something is a daily ritual after all. But no, it was right in the very middle of the floor.
I will try to remember to take pictures if it happens again.