The location of the recovery file will depend on what was configured when the drive was originally encrypted.
It will most likely be some sort of SMB or web share.
You will have to ask whoever originally encrypted the drive where this is.
Also you can only authenticate to DMU with an account that has explicit permissions for recovery and uninstall, which is most likely not your standard user account.
My guess is that this what the error message is related to.
If you don't have the recovery file (which I believe also requires authentication) or a user account with appropriate permissions, I'm afraid there's not much that can be done to recover the files.