Tried to boot up my macbook after a long weekend. Got the inscrutable flashing folder with a question mark. Tried a couple of tips from the internet, like holding option or ‘c’ down, neither of which worked.
Then, hooked up my TimeMachine backup and the recovery console came up on its own, and allowed me to fix the disk (partition table reported the wrong size). Everything was happy.
Kudos, then, Mr. Mac. If you have a time machine handy, it works pretty well. The opposite of kudos for not really telling me that before or after, and for crashing in the first place!