Indeed, this is a commong bug, at least in all my games. Strange it is not reported yet.
Dare I suspect it has been too temptingly useful to all of us? I too have seen this in virtually every game.
Death by enemy violence seems to permanently suffuse that radius of space with friendly probe drones.
Gee, I haven't tried it but if one were to rapidly push out lots of cheap basic overlapping influence bases, maybe with just the free perimeter scanners added, then let the opponents kill them, would you still have permanent reconnaisance into those areas? Does anyone know if the effect lasts beyond reloads? Hmmm...