I see three possibilities:
1) Failure leading to the drone landing.
2) Iran/China jamming/overiding the controls.
3) Intentional grounding.
In scenario 1, the question needs to be asked why wasn’t the drone destroyed. If remote control failed, so might the self-destruct, but other options are available.
In scenario 2, we are in trouble.
In scenario 3, we have the advantage.
One word, “Stuxnet”
The technology for flight is probably not a secret. What is in the computer is. Some Iranian computer geek will download the information and bang.
Knowing the CiIA, they probably put an “to download secret data, use cross connect cable” above the USB port.
Here is one possibility: the CIA has been planning something like this (or a "B" team within the CIA---remember, many of the CIA are lefties). They go to Obama and say, "Just give them the drone." Obama, not wanting to spend the time or energy to figure out if he's being used, or what the implications are, says, "Ummm, ok. I'm going to play golf."