In the process of putting the retainer pins in the bottom of the shoes, one of the smaller pins (I think it is 3/16") which is held in tension with a coil spring escaped from me. I was compressing it with channellock pliers and they slipped. I have been able to find the spring, but the pin must have launched into low-earth orbit.
I hate it when that happens.

And agreed on as soon as you find a replacement, the original one will turn up. It never fails.