I found the other thread. Admittedly the person asking the question was on the next row after the missed yo and this is what suzeeq posted as a resolve:
"Just pick up the yarn between the stitches where it should be. It might be a little tighter and smaller than the others, but after you wash or block it probably not so noticeable."
So, as per Jan's suggestion you can either undo back one row and try this, or, go back the two rows and just get that darn little yo in there!