Correctomundo, seems like seekers do tend to survive the warhead explosion, my understanding of the warhead was incorrect then. Also, recalling the missile chase scene in "Behind Enemy Lines", the seeker part seemed to have been blown away to expose the forward directional warhead, which shot shrapnel all over the F-18. Don't know if it was factually correctly depicted, would be interesting to read up on it.
However, the only problem is, the exact same seeker was visible in the HD video and photo of the wreckage, recorded after the crash. Seems like someone 'dropped' it there immediatly afterwards, eh? If I was forging the evidence, I would gladly add the missing motor of the 1x R-73 & fins of the 1x R-77.
Um none of the referred parts in the photo you quoted is a seeker. As the description reads, the thrust vector control section is being pointed out.