Fixing Dropped Cast-On Stitch (Last One)

I am knitting a hat in the round and used long-tailed cast-on (126 stitches). The first round is P1, K1, and I dropped the last stitch (ack!). Now there is one long piece of string between the needles. I know there must be a way to use that to re-create a stitch there, but I’m lost as to how. The tutorials I see online show how to fix a dropped stitch mid-row, and I haven’t been able to translate that to my situation. Can anyone help??? Thank you in advance!

Welcome to KH!
There’s a video for this that should apply to the last stitch of long tail equally well as to mid-row. I would think that because it’s long tail, there’ll be two strands of yarn rather than one as you describe. If this solution doesn’t work, you could just twist the strand and place it on the needle. However, I would recommend starting over with the cast on.