I've only found this to be true in Word but there is a much faster and more complete way to find all the shortcuts you'll ever need.
1) Open Word
2) Click Tools | Macro | Macros
3) Change Macros In: All active template and documents to Word Commands.
4) Find the Macro call ListCommands
5) Click Run
6) Select All Word Commands

This will create a 26 page document that list every word command and it's corresponding shortcut key (if there is one).

If anyone can figure out how to do this in Excel, PP, Access or Outlook please let me know.