Se. That wonderful thing that apparently makes not-me people not forget their most valuable possesions when they're in plain sight and notice what is in front of their face.
I have vaguely enough tertiary Si to seriously mind not having my favorite pen (could also be a sp thing), but sadly not enough to accurately remember where I put it. I did find it again but it was humilliating, because it was right on the very table I'd sat on the day I lost it. It didn't even fall down or anything.
One day me and my SO - an INTJ - noticed a fairly remote public toilet that he thought seemed like a great makeout spot, so we stayed there for a bit. Sometime during the process, he noticed something tumbling out of his jacket pocket, he grabbed some of it and stuffed it right back.
We leave, head back, but then when we were back in town, we both notice that both out wallets are gone.
All the time he was convinced that it must've fallen out in the bus but we asked the bus drivers, recapitulated our steps, niente!
He was beginning to consider that we might have been robbed and should call the police, ("Not likely we don't have the slightest clue when it happened or proof that it was even stolen, we didn't buy anything or talk to anyone"), it was basically a nightmare scenario because we were on vacation and that was the money for our trip back home, also we'd have to redo the paperwork for our IDs and everything...
Then, just as a last resort/ somethin to try before giving up, I suggested we take a bus back to where
...and there they were, both wallets! They were in plain sight, on a white floor we noticed right as we walked back in!
Yet we must've walked right past them earlier.