Suzeeq is right that you probably did a yarn over that created the hole, then knit 3 rows using that stitch. Since you unraveled the column that held those stitches, there's no way to carry it back up since it's not connected to the rest of the stitches.
Try leaving it as is and pulling and tugging the stitches around it to kind of take up the slack
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IngridKH on Ravelry