We had a similar experience with several taxa in the Lilium conservation collection here. The Winter Spring interface got seriously out of whack on one occasion probably because several species were at their limit of climate tolerances due to our location being so far north at c. 57 degrees 12 minutes. The subsequent Autumn when the bulbs were dug up in expectation of total losses they were almost totally in perfect health and even appeared to have increased in size. Perhaps this might be what has happened to that particular Ornithogalum species. We grow a few of this genus, some Spring flowering others do so in the Autumn but as has been commented on already mini bulbs breaking off from the root plate can take a few years to flower. There is also a problem with lack of flowering through congestion with too many bulbs in the clump, that's aside from the species not being suited to the local climate which is always an inconvenient 'pain'.