The files are saved as *.rcv extension. Saved in ...\Autodesk\Autosketch9 folder where the "..." could be c:\programfiles or wherever you installed to. In Vista I install to C:\Users\Public\Autodesk\Autosketch9 for example
The default is probably c:\ProgramFiles\Autodesk\Autosketch9, but you could always search for *.rcv files
Doesn't the program prompt you when you first start up that you have Crash Recovery files available to recover?