Ack! Chrome crashed and didn't ask me if I wanted to restore when it came back (as it updated itself?)
Maybe not a problem if you have a few tabs open - but I'm a tab-aholic; I have 15 windows open, each with an average of 10 tabs. You try remembering what all those 150 tabs were!
Anyway, after a lot of google searching (who would have thought that "chrome restore session" & "chrome has lost my last session" would not turn up useful tips), I finally stumbled upon http://bashelton.com/2011/06/how-to-unclobber-your-last-session-in-google-chrome/ - it saved my life (well, session at least)