It seems more likely to me that the OP's M+B number was attached to the booking in error, which then auto-filled the e-mail field and sent notifications out. Given no original booking e-mail was received, the likelihood is that this happened sometime afterwards.
This could have done by the person making the booking, but equally it could have been mis-keyed by an A3 agent ... and at this stage I would strongly suspect the OP will not ever get to find out.