How to find out when and where backup recovery password was set for iPhone backups?

I had to get my iPhone camera repaired and I had to back it up and erase it so that the repair shop could access the camera app without being able to access my data. After picking it up after the repairs I wanted to restore the backup but had to enter a password. All passwords I could think of are wrong. iCloud password, Mac password, iPhone passwords, pins, and all other sorts of passwords.

When and where was this hellish password set? There was no prompt asking me for a password before backing up my phone. I have spent hours entering passwords and nothing works. It is unbelievable that this is not using my Apple password, Mac password or any other device password.

I am starting to lose it. The thought of me losing all my data forever is just crushing me right now 🤢

Is there anything I can do to either recover the password or at least find out when and where it was set so that I can at least get a hint or reminder as to what the password could be?

Edit:

I should mention that I did look through my keychain and couldn't find anything with "Iphone backup" or "iOS backup". My Macbook pro is from late 2017 and I never did an iphone backup before. I really don't remember ever setting a password :/

A friend told me to call Apple. There is probably no chance they can help me in this, right?

The password used for local iPhone backups is set when enabling encrypted backups. When checking the box to use encrypted backups, a dialog asks you to enter a new password. This is independent to your Apple ID or other passwords.

Your Mac stores the password in the login Keychain and uses it for future backups. To get the password from the Keychain, open Keychain Access.app, search for ‘iPhone backup’ or ‘iOS backup’ and open the item, then choose ‘Show password’ and enter your Mac account password to view the backup password.