CRASHED WITHOUT AUTO-SAVE

First, although it may not be much comfort, rebuilding what took you 4 hrs to do, will not take nearly as long.  This is the voice of experience speaking.  I've seen this happen over a long professional career and it never takes as long to redo something that you've already done.  It's not a common occurence but it has happened to me in Avid and FCP 1 - 7.   But are you sure that somehow or other the autosaves don't exist some where on your system?  Have you done a system wide search for your project name?   autosaves usually append the time to your project file name, so a search for your premiere project file name might turn up the autosaves.  It's never happened to me in Premiere, but in finalcutpro I did occasionally experience a failure of autosave when the preferences became corrupted.  

In the future, it's never a bad idea to occasionally do a manual save of your project.  And since this has happened once, it may be a symptom of an underlying problem with your system and might be a good idea to test the autosave feature before proceeding on this or another project...