Have been knitting 9 stitches in double moss stitch, for front edge and now the pattern says knit 5th and 6th together to form a buttonhole, knit to end, then on the way back there’s no indication about how the stitch is recovered for subsequent rows, yet it says carry on in pattern with 9 stitches in double moss stitch, making the band the same width…

Welcome to KH!
Sounds like this should be a yarn over buttonhole. The pattern should have you knit the 5th and 6th sts together and then yarn over. On the next row, you’ll have the sts needed to complete the pattern.
What pattern are you making? Can you give us a name or a link to it?