I have a CFL in the bathroom that went out on me. I’ve been too lazy to change it because there are other bulbs that are working. Well after a couple weeks, it magically decided to turn back on. It’s nowhere that it would be jostled or anything, so I found that weird.
Maybe an electrode with a lot of age on it was nearly burned up and one more flip on managed to blast a little clean spot on it.
Maybe you had a short in your ballast that got hot enough to change material properties a little and not become a short anymore.
Maybe your ballast was loose and had an open line and it just managed to wiggle enough to work again.
Maybe your ballast is partially shorted and ineffective at certain voltages and your temperature in the room is now cold enough to work with a lower potential ballast.
Maybe you had a shorted cap that leaked and then burned itself the rest of the way out and is now open.