So, this morning i looked things over, and suddenly realized that the broken thread is in the middle of a section that used the one color of yarn that i ran out of when making the warp. I don't think there's an easy way to fix this without at least one decent sized extra piece of the same warp yarn, so i'm going to simply remove that thread from the piece, and proceed as if it was never there. it's part of a fairly wide band of one color, right in the middle, so i don't really think it will be a big deal. if it turns out this was a big mistake, i will post again when i discover the truth.
Thank you both for the comments.