Don't give up yet!
If you had telemetry going then your log will give you a lot of info on where it was heading or maybe even show you exactly where it is at.
Go back through and try to figure out what went wrong. Could you have switched into AUTO accidentally?
Where did you power up and set home position for that flying session? That's where RTL would take it.
How many Ah capacity left in the battery when this happened, if not much and it was climbing with a lot of power, then it couldn't have gone far.
I don't know what the terrain is like where you were flying, but look at a map and estimate a radius of possibility for where it could have gone. Put on your boots and go hiking. Like a lost cat they are always closer than you imagine.
Marvin,sorry for your loss as others have said they are often closer than you think, good luck searching.
@Paul I don't think his hardware fail sounds like the switch selection was incorrect.
You cannot just go out and expect the GPS constellation to be perfectly positioned above your mission site. What does that mean. It means there might not be enough over the horizon or they might be horribly placed.
I check what might be overhead before I fly.
I had exactly the same problem ... lucky there was a tree in it's way so it crashed!! I had a Log file ... still don't know what when wrong. See my post : http://diydrones.com/forum/topics/first-flight-crashed?xg_source=ac...