Duane - my 'guess' - and I'm not a botanist by any means - is that there were probably enough nutrients, sugars, starches, etc. in the main root for it to keep growing some after it became severed from the bulb. But it won't keep growing like this (I think you dug your lilies 6 weeks or so ago?) and it will eventually rot. For it to produce a new bulb there needs to be a piece of the basal plate still attached, just like you have when producing new bulbs from scales. Hope this helps.
