Thanks for the great responses
Sadly, the lucy bag starts in a circle and increases out, so following the original cast on tail didn't work, and I was already approx 80 rows up on the bag, so I'm taking my chances that it won't make a difference in the end result if I'm off a few (or 20
!) stitches from my start of round.
I like the idea of the embroidery floss, but I'm not sure I understand exactly how you are using it. Is it your end of round marker loop, and then as you come around to it again do you catch the tail?