The warhead on the missile is designed to cause an annular blast throwing its folded continuous rod outwards, the explosive force travelling axially towards the seeker head will be significantly reduced. The bolted structure of the seeker is pretty strong, it would not be damaged easily.
Other photos taken near the crash site show an area with 2 parallel low concrete walls quite close together, it is possible that the seeker could have lodged in the airframe and then fallen out during the ground impact sequence.
This is a statement of possibility, like everyone else here I have no magical insight.