If the device is in Apple Business/School Manager, you can simply call AppleCare, explain the situation, and they will look up the device to confirm it is indeed in ABM/ASM and then assist from there.
If the device is not in ABM/ASM, but you have the original purchase receipt, you can go to the Apple Store and they can help you. You may be able to get help over the phone, but I've never tried that method.
If the device is not in ABM/ASM, and you don't have the original purchase receipt, you will need the employee to either release the device from their iCloud Find My, come in and enter the password and disable for you, or give you the password. If the employee is unable or unwilling to assist, you have a brick.