Any proper use of encryption will not store the key in a config file. While a hash might be stored, it's one way, so knowing the hash will not allow for recovery of the password, only that the entered password's hash matches the stored hash, and therefore the proper password was entered.
You will need to use the original app as it most likely uses a proprietary structure to encrypt the image file. The only option you have at this point is to try to remember the password used as well designed AES encryption renders the original contents unrecoverable by design unless the exact password is used.
Use encryption to protect yourself but expect total data loss unless you have a proper password management system in place to prevent losing/forgetting the password/encryption key.
Since this is Photo Locker Pro, produced by Handy Apps, perusing their Google Store and online website FAQ delivers the following information.
- With the optional PIN recovery feature, you won't lose your precious files even if you forgot your PIN code.
- The recovery email address is not an username to restore data. It is only used to retrieve your PIN in the event that you have forgotten it.
It's time to contact their support desk (support at handy-apps.com) and see if they can help you finish the recovery process.