Basically as the title says.
I can't recall doing anything particularly interesting which may have led to them deciding to abandon me. Likewise, while it may be me acting a dunce, I can't see an easy way to bring them back. I've tried wiping my cookies on the off chance that made a difference... it didn't.
It's not the end of the world as I'm able to put them in manually and/or quote other messages that contain the code I need but it's a bit of a hassle.