Can you dig out the 'other end' of the yarn and use that to pick up the other stitches?
You will need to cut it, eventually.
I have a method for working upwards after a split in the work, usually when doing horizontal buttonholes on front facing which is picked up from the margin of the work.
Often, the instructions say to cast off 3 or 4 stitches and cast on in the next row. This leaves a hole that gapes.
To do a buttonhole, after say 6 stitches from the hemline, work those 6 stitches + the number of stitches to the next buttonhole (say, 8 more stitches).
Turn, knit to the place where the first buttonhole will be. Wrap the yarn around the right needle to match half the number of rows which will form the hole - say 2 or 3 times
*Next row: knit together the first stitch of the lowest buttonhole PLUS the first wrap, work to the 2nd buttonhole place, turn, work back to buttonhole space.*
Repeat from * to * until the lowest buttonhole is completed. By wrapping yarn around the right needle, and knitting the yarn together with the next stitch, this means that a split of whatever size is needed can be done without cutting the yarn, as in the slotted neck scarf.
If the holes are made in a buttonhole band, the turns should be repeated to the very end, with the latter part being worked to the same depth as the area without buttonholes.
All this might look complicated, but try it on just a short piece of work - say over 40 stitches with 2 buttonholes. The result is much nicer than the cast-off and cast-on method.