Thanks for that info and choosing the Apple Support Communities. If I understand correctly, you are missing some Favorites that you added to the Maps app. If you haven't already, restart your iPhone as the shut down and start up process is important to keep the iOS software running properly. iOS clears cached data and does other system optimizations when you turn your device off and on. Once your iPhone is back on, check for your missing Favorites in the Maps app. If they are still missing, your next step would be to restore from a recent backup when you still had these Favorites.
Restart your iPhone, iPad, or iPod touch
Restore your iPhone, iPad, or iPod touch from a backup
Cheers!