Hi Bob, thanks for giving this your attention.

Yes, I tried shutting down etc, and I've tried looking in the places that are mentioned in those links, I'm not able to locate anything, which is odd as I am pretty sure all of the songs are still on the machine.

I'm not a regular Mac user so I may be doing something wrong; I did a search for .html and .irb files 'This Mac' in the search function, and found some .html songs I had exported onto the desktop but nothing else, and I did the search for iReal Pro itself and found the app in /Applications, but but I still can't locate the folder with the songs. Also tried these:
~/Library/Preferences/com.massimobiolcati.irealbookmac.plist
~/Library/Application Support/ireal b/UserSongs.plist

Grant