Esprit de l'escalier

I need to find out who the mystery Snapple Cap contributor is! There is a really stealth cap contributor who I can’t, for the life of me, snag to say thank you. This person has put around 13 caps in the contribution box when I’m not looking. I can always hear the donation taking place…but EVERY TIME…when I get to the door and peek my head out…there’s no one to be found. I’m up to 81 caps after the mystery donor made his last contribution.
I’m convinced this charitable spirit must have some sort of previous experience…because this is obviously not a rookie we’re dealing with. The other day I was studying on the sofa…in my usual position. The door was cracked open (which usually means “I need to study, but I don’t want to close the door all the way because I’m secretly willing someone to come by and distract me from this academic vice called a text book). I was in the middle of reading about dualistic traditions when I hear the familiar clinging of Snapple caps! I jump up, leap over the back of the sofa and slide across the kitchen floor to the door. I literally fall into the hallway with my book still in hand. Did I catch even a glimpse? No such luck. But one of these days…*drifting off* one of these days I will cross paths with the noble contributor…this ROBBIN Hood of Snapple cap currency…and I will give him/her props and a hearty pat on the back.