Apple Wallet

From your Home Screen, swipe left until you get to the App Library.

Swipe downward and you'll get an alphabetical list of your apps.

Locate the app in the list or type the app name into the search field

Once you've located the app, tap/hold then drag it and it'll pop out to your Home Screen

Organize the Home Screen and App Library on your iPhone - Apple Support

Corwin1408 Said:

"Apple Wallet: I inadvertently removed my Apple Wallet from the Home Screen. How do I get it back on the Home Screen?"

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Perform Two Things:

A. Start with a Restart:

Restart your iPhone, and see if it then is fixed.

Then...

B. Reset the Home Screen Layout...

Go Here: Move and organize apps on iPhone - Apple Support

Scroll to: Reset the Home Screen and Apps to their Original Layout

1. Go to: Settings
2. Tap: General
3. Tap: Reset
4. Tap: Reset Home Screen Layout