I did the same and bought half a dozen of them. Still always seem to be hunting for one if I don't have my saw box handy. My Echo scrench is the one I have to keep an eye on. Only 10mm version I have. I need to get some bright orange paint and coat them...might help.
I have lost a bunch as well I put one in the saw case one in the truck and a few in the garage and basement. I also spray paint them a bright color so if I drop it I have a better chance of finding it
I have a cardboard box that the saw, jug of bar oil, saw gas, chain maintenance tools, wrench and other saw accessories go in. I have 3 other wrenches in my tool box.