Not sure, but you can use a free program called Process Monitor to find out: http://technet.microsoft.com/en-us/sysinternals/bb896645.aspx
It shows ALL hard drive activity (reads/writes), which will show thousands of lines updated every second. So set the program to only show activity from the game once it's running. Use Right click "include only" to do this.
Then get to a point in the game where it saves. Then check the program to see where the location where it saved.
Yay! I did it! Just do a system search for the file: ast_save and have your friend copy that file to the same place on their PC. Or if you want it the easy way and want me to do it for you: C:\Program Files (x86)\Steam\userdata\75595729\212480\remote