Unless you used the ZIP option, there is no specific file extension. The files will be reproduced with the usual SW extensions, in whichever folder you chose.
If you tried to make a zip file, there's more than a few ways to screw it up and not realize.
Heck, there's ways to screw up a regular pack-and-go. Hitting <ESC> or <Return> at the wrong moment can knock you out.