As I pointed out, it's not one missing shot. When I synched up the audio, it showed that the shot before the closeup cut out early, and the closeup shot was joined in progress. The music is scored to the full version of the scene, and the music splice on your recording seems sloppy and abrupt.
If some accident occurred and that section got boogered up, the projectionist might have had to cut it out just so they could continue running the print. 70mm was expensive, so it was probably a lot harder to get a replacement print, especially on short notice.
Several seconds of footage being spliced out in the middle of a reel isn't completely unfeasible. A couple years ago, I saw a 70mm print of Ghostbusters, provided by Sony, where Bill Murray's line "So if we think of J. Edgar Hoover, J. Edgar Hoover's gonna show up and destroy us" was clipped out. Obviously, at some point down the line, that section took some kind of damage that resulted in it being cut out.
Admittedly, that was a 26-year-old print, and this ESB screening was during original release in 1980, but I'm just illustrating that it's not completely out of the realm of possibility that those missing 5 seconds were missing from that print only.
I second your interest in hearing another in-theater recording of a 70mm screening.