How did my fingerprint I’d get lost updating to 15.5? It won’t work in the App Store.

I am not sure which ID you are referring to...

Screen Lock - Passcode

Following this process is the only way out if your iPhone is disabled. The steps given in this link will help you reset the passcode -> If you forgot the passcode for your iPhone, iPad, or iPod touch, or your ...

Apple ID & Password

If you do not remember the Apple ID Password then follow the steps given in this Apple Article -> If you forgot your Apple ID password - Apple Support

If you do not remember the Apple ID then follow the steps given in this Apple Article -> If you forgot your Apple ID - Apple Support

Activation Lock

If you are the owner or the owner has shared all information with you then to open Activation Lock:- If it is Activation locked, read here --> Turn off Activation Lock - Apple Support Activation Lock for iPhone, iPad, and iPod touch - Apple Support

Learn how to remove a device from a previous owner's account.

If you are not the owner and do not have the Apple ID and Password then there is no way that you can get into this iPhone unless the original owner shares the Apple ID and password with you. If you are lucky you can get into this iPhone if they (owner) accidentally remove the device from their Apple ID.

Carrier Lock:- Request your iPhone’s original Carrier to unlock your iPhone and if they agree and do it, then you may know the further process here --> How to unlock your iPhone for use with a different carrier ...

Apple ID Lock

If you can't unlock your Apple ID

If you use security questions with your Apple ID, or if you don't have access to a trusted device or phone number, go to iforgot.apple.com. Then you can unlock your account with your existing password or reset your password.

If your Apple ID is locked or disabled - Apple Support

Apple Cash

If your account is restricted, you can still transfer your Apple Cash balance to your bank or use it to make purchases in stores, within apps, and on the web. If your account is locked, you can't use Apple Cash to make purchases; add, send and receive money; or transfer the money in your account.

If your Apple Cash account is restricted or locked - Apple ...

Turn off Touch ID and turn it on again, after that set up a "new" fingerprint. My mom had this same issue while updating her iPhone 6S to 15.5. This is how I fixed it for her

Add your fingerprint again as Touch ID