There is a way to do a purl cast on to compensate for not having enough yarn for the long-tail, but I've yet to learn how to do it. (I've seen Lily Chin demonstrate it on Knitty Gritty.)
Until I learn it, and to ensure I have enough yarn for the long-tail, I wrap the yarn around the needle as many times as I need stitches. (20 wraps for 20 stitches, for example). Then I add a little extra (maybe 6 inches) just in case.
Sorry you didn't have enough yarn for the cast-on; it's really frustrating, I know!
When I have a lot of stitches, I use two balls--one for the strand and one for the tail. I never run out, and I just cut one when I'm done. I either felt the ends together if it's wool, or tie the dreaded knot.
"Trust the pattern!"
Time flies like an arrow, but fruit flies like a banana.
Hop aboard while we follow the cloud-covered van of knitting harmony, man!! Woooo!! --Hedgehog
Thanks so much for that link! That's exactly what I needed. I am impatient (obviously, or I wouldn't have ended up with toos hort of a tail), so I went ahead and re-cast on with a much longer tail and that worked out OK.
The purling on technique rocks, though, I'll have to remember that!