Were you instructed to move some of the stitches to a spare needle? Can you link to your pattern? That would be a big help.
It looks like you are to be knitting in the round for the ribbing after the seams are done. It might be possible to leave one seam open and knit the ribbing flat and then seam it as part of the neck seam.
I really need to see your pattern, maybe others will understand without it as they are much more experienced than I.
Happiness is catching that dropped stitch while it's still fixable..