Did you look in the correct library - there are three different libraries where things are installed.
The ProAppSystemID file shoul be located in the public System Library directly on your MacintoshHD:
Your MacintoshHD > Library > Applications Support > ProAppsSystemID
If it really is not there, have a look at this post:
Thanks heaps! After about 15 attempts I got it to work... The file lived in the temp folder (I had to open a terminal window to find it). Every time I placed it back into Pro Apps folder it didn't work as Aperture would create another ProAppSystemID file in the temp folder again, and it wouldn't save the latest file in the Pro Apps folder. Eventually it worked though, and seems to be working now after 3 mac re-starts.... Fingers crossed it stay that way!