Good for you! A friend did the same thing a few years ago. She left it in a cup of water, left for France for a month, and came home to a sprout! It's potted and doing well; no fruit for a long time though I hear...
Her theory is that they like really calm water. She's tried for years to get one to sprout but no luck. Then this one gets forgotten and VIOLA! A watched pot never boils, I guess! A watched Avo seed never sprouts!