Not OP, but I too loose sunglasses all the time. I'm pretty sure those are mine. Now as soon as I figure out what Juliets are and where "Yosemite backcountry" is, I'll prove it to you.

Actually, I've been able to hang onto my most recent pair for well over a year now. The trick is never taking them out of the car. The way they get lost is you wear them from your car into some house and take them off.