Inexpensive locator beeper just for you
I'm on my third mQx and am determined to not lose this one. To that end I installed a beeper that only weighs a few grams. You can specify from the builder what start time you want and it beeps until the battery goes dead from that point onward. In my case, it's a 15 minute delay from battery connection to beep start. Since I get 9 minutes flying time, that means if I lose it, there's another six minutes to wait and perhaps to get closer to the area.
I'm also considering to build a plastic parabolic sound collector
to make it easier to hear the beeping should it be necessary.
If you find your copter, the battery is going to be very very puffy and of course, useless. Mine was in a tree for 24 hours.