Most of us have seen this. As soon as the bulbs get warm enough, they start growing, which is why distributors store them refrigerated. If bulbs are long in transit to the buyer, they'll start growing while in the bag.

What is going to happen to that bulb....likely it will be fine. If no one buys it, it will die after it expends all of it's internal resources. If someone plants it, it will grow roots and be fine.

Why did it start growing....it got warm enough. The bulb has everything it needs stored inside for growing scapes and flowers. Look at posts here about bulbs dipped in wax.
K