They can take a while to sprout. Just plant them in soil next time don't put them in wet plastic bags. You may have broken the root when you transplanted it, but it may grow a new root. I planted four this year, three from one tree and one from another. The three from one tree all sprouted maybe a month earlier than the other, but that one is now the biggest. Your one survivor is looking good though, much bigger than mine, planted about the same time.