Help! - Forgot to knit stitches with waste yarn

I just finished a second mitt which is made with “afterthought thumbs” - you knit 8 stitches with a waste yarn, transfer them back to the left needles and reknit them with the original yarn. When the main mitt is finished the waste yarn is removed and the stitches picked up and the thumb is knitted. Except I forgot to do this on the 2nd mitten … and now I have a tube … Other than ripping, is there a way to get those stitches? Thanks in advance!

You could very carefully cut the yarn where the thumb should be, putting the upper and lower sts on a needle and leave a bit of a tail on both sides of the knitting that you can weave in later.