Thank you for the encouragement, Bella!
All of my games are on the same drive, so I don't know why some of them didn't appear in the Game Manager. I didn't ask the Customer Service person I "chatted" with online yesterday why that might have occurred, just how to fix it.
With respect to the games that are on my Purchase History but not on the Game Manager, the fix is not technically difficult, just a little time-consuming.
I am going down the list of purchased games game by game on the Purchase History and checking to see if they appear in the Game Manager.
For those that do not appear in the Game Manager, I am uninstalling them on my computer and then re-downloading and re-installing from the Purchase History page.
Viola! Now they appear in the Game Manager.
I only had time to uninstall and re-install about four of the "missing" games yesterday so I haven't had a chance yet to see if I lost prior game progress, but I'm kind of assuming the uninstall from my computer may result in that. Still, it's worth it to me to have them in the Game Manager as that is what I usually scan to see what game I might feel like playing, and I want them all to be there.
With respect to the "missing" James Patterson's Women's Murder Club game, it wasn't missing from the Purchase History at all!
The list on the Purchase History was alphabetical and while one game was listed under "J" for "James Patterson" the other was listed at the bottom of the page under "W" for "Women's Murder Club," so happy news there!
Hope this helps anyone else who may have the same problem!