If you drop it off the needles, it will run down creating a ladder, you can just pull it back up using the slack in the ladder.
But if you dropped it many rows ago and just noticed, then on the rows after you dropped the stitch, you would have been knitting normally and there is no slack to create a new column of stitches with.
So if you don't want to unravel the work after the dropped stitch, then just fix the ladder as far as it goes, and you basically sew that stitch into the knitting at the top of the column so that it doesn't fall back down.
In fact I would probably sew in with matching sewing cotton on the back, small stitches etc., rather than attach by weaving in ends. Your choice.