I'm sure the military has the right terms for this...

It's probably a blast-related brain injury. It may or may not be permanent, it could be purely neurological from the concussion? I doubt anything is just one thing though, and the trauma certainly has had cognitive effects as well.

It could be that the head trauma from the blast has messed up some of the wiring and needs some time to regain itself...similar to our "normal" concussion symptoms where it takes us a while to get it altogether. I sure hope it's only time he needs...

So hopefully with therapies (physical and psychotherapy) he will be able to sense and know he didn't lose his legs and regain the use of them.