If (like you) he can't see the recovered SRB, why has he now
leapt so fast to NASA's "foam" conclusion?

1: Because the video clearly shows the foam breaking off the ET, and
the post-separation photos clearly show the hole where the foam was, in
the same shape and size as the chunk seen flying off. See:
http://www.spaceref.com/news/viewsr.html?pid=17514

2: Because there's nothing equivalent to break off the RSRM.