my last van key...VANISHED.

I decided to drop off a box at Goodwill that's been in the back of our van for a while now after I ran some errands with the kids this morning. I took my single van key-- not on a chain, mind you, as I lost my entire chain of keys somewhere between Wisconsin and here on our way home two weeks ago-- unlocked the back van gate, got my box out, gave it to the man collecting donations and got back into my van. Jack then asked to be unclothed of his especially-warm, layered monkey costume (which he needed to wear on our excursion) since the back-seat was now super-toasty in the sun (70 degrees outside). I acquiesced and then turned back around to start the van. My key? Who in the world knows? Please tell me where my key is.
For an hour, I turned our van upside down. I looked in the shoes that had been on my childrens' feet the entire time, in the glove box, which had not been opened that day, on the complete other side of the van. I looked through the box of stuff I had donated, in both kids' clothing, under all van seats. I climbed over the seats multiple times, scouring ever nook and cranny and dicovered that our van is a pretty filthy place. I kept thinking, It has to be here somewhere. How do I always manage to do this? (sometimes it's cellphones). I think I do get it honestly-- I remember digging through the back of my mom's van on a similar key-vanishing occasion.
Nevertheless, I called Mike at work- several times, on random strangers' phones, until he was finally at his desk. And he came and entrusted me with his van key-- the very last (out of three) one. What a silly thing to do. I suppose this would be an even better story if I ended up losing that one somehow on the way home, but that intelligent man took it from me and placed it back on his chain as soon as we pulled in front of our house. I hope he lets me borrow it again so the kids and I are able to get out once in a while. We really need to get a copy made before his vanishes too.