I did a breakdown of the SA Kirby pages so far as to their inventory/ provenance status --can't see if any of them are signed by Jack yet.
Amazing Adventures 6, pg 10: Marvel had 23 pages in 1980. Kirby drew 13 pages in this issue and was returned 8 in 1987. Did some or all of the missing 5 go to the estate of the inker, George Klein, or accidentally to Ayers? At any rate it's possible this page passed through Kirby's possession.
FF 34, pg 19: Marvel had 21 pages in 1980, returned 13 to Kirby in 1987. But which ones?
FF 78, p19: This whole book was missing at the time of the 1980 inventory, and so, naturally, no pages were ever returned to Kirby.
TTA 7, 5pg complete story: Marvel had 18 pages from the issue in 1980, none were returned to Kirby (an obvious problem with many page provenances is that neither the 1980 inventory NOR the 1987 return list specify WHICH pages specifically, so these 5 pages could have been missing even before 1980).