[kijin]

That looks like a rather flat trapezoid for something that fell from high above.

With a fast-moving object, we can usually tell its trajectory across the map much more accurately than we can tell where along that trajectory it impacted the ground. See: MH370.

[daemonologist]

Maybe fits the "DoD is shooting something at some kind of incoming drone" explanation - they know they're shooting _from_ the top of the trapezoid but in terms of direction, only that they're vaguely facing south. (Doesn't really explain why the TFR doesn't extend into Mexico though.)

[jjk166]

The area they would expect to find it would be much narrower than the area they would expect a plane overhead to be able to observe it.