Quick fix: Use a crochet hook to pick up the dropped stitch, matching the column — knit stitches picked up from front, purl stitches from back.
What you are seeing
A stitch slipped off and unravelled. In ribbing this is trickier than stockinette because you must match the pattern — wrong direction leaves a twisted or mismatched stitch.
Why it happens
- Yarn slips off needle while moving between knit and purl
- Needle tip bumps stitch when repositioning yarn
- Uneven tension between knit and purl stitches
Fix it now
- Pin the dropped stitch with a safety pin so it can't drop further.
- Identify the column — knit columns show V shapes, purl columns show bumps.
- For a knit column: insert hook front to back through the loop, catch the ladder rung, pull through.
- For a purl column: turn your work so that column faces you as a knit column and pick it up the same way, then turn back.
- Repeat for each rung. Check the stitch matches its column after every row.
- Return to needle untwisted.
Prevent it next time
- Move yarn slowly between knit and purl
- Use blunter needle tips for ribbing
- Add a lifeline every 15 rows