Unfortunatelly I don't think so. It sounds like you have configured a computer for home use with mandatory Microsoft Account and your husband used his employee working email adress for MS account registeration. Only way is somehow try to recover his MS Account, but if he does not have access to his email anymore, it could be difficult.
Anyway, Bitlocker recovery keys always goes behind device registeration in MS Account, when a home user installs a Windows computer and applies his MS account while installation.