Please find below my responses:
Check iCloud Sync: Make sure that you are signed in to iCloud on your iPhone, and that iCloud syncing is turned on for Maps. To do this, go to Settings > [your name] > iCloud, and make sure that the toggle next to Maps is turned on. If it is turned off, turn it on and wait for a few minutes to see if your favorites and guides reappear.
SM: Was not turned off, shows enabled
Check Apple ID: Ensure that you are signed in with the correct Apple ID on your iPhone. To check this, go to Settings > [your name] and verify that you are signed in with the correct Apple ID.
SM: Correct, no changes
Need more info,
If you have multiple devices the same may have been deleted on some other device (Mac/iPad etc.
SM: Yes deleted on other devices too
Are you sharing your Apple ID with others?
SM: No