That's my theory until they find it.

so...

Hard to tell here what they are saying. The plane would be hard to see on alot of radars, but it would likely be flying with a transponder so that it could be tracked. Did the F-35 turn off it's transponder? Was it flying to low to be detected? Was it descending? Ascending? Did it change direction prior to "disappearing"? Did they try to contact it? Were they ever in contact with it? Oh, and whose F-35 is it? Japan's? Did they send out a plane to look for it?

http://time.com/5567195/japan-f-35-jet-crash/

(snip)
Pieces from the wreckage a Japanese fighter jet that crashed into the Pacific Ocean Tuesday have been found, Japan’s Self-Defense Force confirmed a day after the incident.

Officials said the relatively new F-35A was on a training mission with three other jets of the same model when contact was lost, according to Japan’s national broadcaster NHK.

Japanese Defense Minister Takeshi Iwaya said the jet, which flew from the Misawa Air Base in Aomori Prefecture, lost radar contact just before 7:30 p.m. Tuesday. The plane was around 85 miles east of the coast. Just before the crash, the pilot contacted the other jets in an attempt to cancel the mission, according to officials.

Patrol aircrafts and ships were deployed to search for the missing F-35A after the disappearance. On Wednesday, search teams recovered debris from the jet, including parts of the tail, but Japanese and U.S. forces are continuing to look for the missing pilot.
(snip)