Is the document still open? If it is, first thing to try is an export to .idml (see http://forums.adobe.com/thread/526991). If you are not able to export either, you have a chance, not a certainty, of recovery by force quitting ID and restarting. I know this is a very scary idea, but ID's auto-recovery is actually the best in the business. If the recovery data is not corrupt ID will restart and open any documents that you were working on at the last recovery state, which is generally not more than an action or two removed from the last thing you did. Resave with a new name. DO NOT OVERWRITE the other file, then try the export again. If you've already closed the file or ID there's nothing you can do to recover the lost work.