It's just not plausible. If the Russians, with their much more sophisticated and advanced electronics can't tag our drones, I seriously doubt Iran, who hasn't even developed a nuclear weapon yet, could. Iran is literally where the USA was back around 1942. Do you really think in 1942 we had the technology to take over a remote control plane whose electronics alone cost many many many millions of dollars? I doubt it.
And it wouldn't impress me much if Iran shot down a drone. They fly about the same speed as a Cessna 182 and have the radar cross section of a school bus. Not much to brag about there. And this is IF they shot it down, which I seriously doubt. The Iraqis used a Mig 25 to shoot one down, ironically on September 11, 2001. They aren't hard to shoot. It's like a duck hunter going out and blowing buzzards out the sky.