Interesting! I don't recall ever having had that happen, but then, I rarely dig them once they're in the ground. But I think I'd see little foliage around the mother bulb if it had occurred. This has me thinking of a thread Leftwood started on DG about planting bulbs shallowly to promote increase- do you recall how deeply you planted them? Another idea comes to mind; I've read the basal plate of some bulbs can be scored, and that will promote bulblet formation. Perhaps the bulb received an injury at the basal plate at harvest.
