At my current job I normally do not handle IT support but since I have a history of doing support my colleagues sometimes asks me for help. Todays issue was a computer with a new motherboard that was missing a Bitlocker Recovery Key.
We are a small company so we do not have out own infrastructure and are relying on Azure AD. When you join a Bitlocker encrypted device to Azure AD the key is stored in you user account in the Azure portal. To retrieve it, log in to the Azure Portal, goto Azure Active Directory and open the User you are looking for. In the user properties go to devices and find the key. If the user has more than one key you can use the Bitlocker Key ID to locate the correct key.