Was the dimmer switch ever changed before? It should make a click sound when you turn it all the way counterclockwise that turns the dome light on. Mine did the same thing with the dimming of the dash lights too so after I changed the switch the lights dimmed and the dome light worked again. Did you try installing a new bulb?
As far as I know the dimmer switch was never replaced and the dimmer does make a click when I turn the brightness all the way up, and I tried a different bulb that I know is working but still didn't work, but to be on the safe side I'm going to order a couple different bulbs, I would be a little embarrassed if it was as simple as a burnt out bulb but I would also be relieved that its a simple and easy fix, the reason I don't think its just a burnt out bulb is the dead battery issue I seemed to have at the same exact time as the bulb not working, would a burnt out bulb cause a parasitic draw enough to drain a battery in 12 hrs?
Previously I have been driving around with the #8 fuse removed from the fuse box (which eliminated my cars battery dying) and I am going to reinstall the #8 fuse in the fuse box which gives me back my radio which I did install myself....over 4 years ago and never had a problem with it ever before, so I really Highly doubt thats the issue.
And i'm going to take off the dome light housing as a whole to see if my battery dies any time soon, while I wait for the bulbs I ordered to arrive.