The folder where recovered files are stored depends on your system:
- Under Windows Vista / 7 / 8, it's C:\Users\user\AppData\Roaming\eTeks\Sweet Home 3D\recovery folder
- Under Windows XP and previous versions of Windows, it's C:\Documents and Settings\user\Application Data\eTeks\Sweet Home 3D\recovery folder
- Under Mac OS X, it's the Library/Application Support/eTeks/Sweet Home 3D/recovery subfolder of your user folder
- Under Linux, it's .eteks/sweethome3d/recovery subfolder of your user folder
- With the portable version, it's data/recovery subfolder of Sweet Home 3D folder.

Did you try to increase the max memory to see if it works better?