I'm with HandyFamily! Just drop the stitches that the buttonhole is made over (carefully and slowly) back to the row where the buttonhole is meant to be. Use a crochet hook of the appropriate size, work the button hole then pick the dropped stitches back up to your current row. Being stockinette stitch is used it shouldn't be too difficult.
I went back 30 rows to correct a wrong stitch once, rather than ripping everything back to the error. It didn't take that long either. Certainly less time than it would have taken to rip back the 30 rows, fix the error and reknit those 30 rows.
I went back 30 rows to correct a wrong stitch once, rather than ripping everything back to the error. It didn't take that long either. Certainly less time than it would have taken to rip back the 30 rows, fix the error and reknit those 30 rows.