it is not easy to recover everything, but you can do the following:
1) the auto-saved .psm file should be in the same directory where your swap files are. on macosx this is in /tmp by default. i am not sure about windows. if you copy that PSM file out of that directory you can then load it the way you would load any other xpsm file. therefore you can get all your process icons back, assuming you had PSM auto-save turned on.
2) you can recover a particular step in the history of some image. in theory it's possible to recover the whole "visual" history of an image, but the actual history is lost. the problem is that you have to somehow guess at which .swp file is relevant to you, say by looking at the timestamps in the /tmp directory. anyway the trick is to create a dummy image with pixelmath or by opening another image, then apply some operation to it, like invert. a new .swp file will then be created which holds the original state of that dummy file. the next trick is to copy over that .swp file with the .swp file that you're interested in, and then undo the invert. that will cause PI to load the .swp file again, but instead of loading the pre-invert state, it ends up loading the .swp image you copied. so then you can save your file out in some other format.
you could apply multiple bogus operations to your dummy file and then copy all the .swp files belonging to some image that you were working on, but the problem is figuring out which .swp files on disk belongs to a particular image's history. lots of trial and error, and not too fun.
after a crash, i usually copy all the .swp files out of the /tmp directory just to be safe. in the OSX terminal you can force copied files to retain their original creation date; not sure what happens on windows when you copy a file in the file explorer.
since you were working on a mosaic, you could probably use the sizes of the .swp files to determine which ones are part of the mosaic... all the largest ones are probably the ones you are interested in.
rob
edit: i was just looking at swap files that were created, and they do seem to have part of the image name in them, so identifying which swap file is which is perhaps not as hard as i remembered. for me anyway it's been a very long time since PI has crashed on me so i've forgotten the details.
