I suppose the operator must have come on the line telling him they had patched up the line, then he listens and hears some sounds. As for the call log, he'll just say he wasn't asked to make one, and the conspiracy theorists will say it's all been hushed up.
That's not what he says, he says, "From what I remember, someone phoned 999 from inside the farmhouse ........ the caller hadn't spoken to him, but he recalled hearing what might have been muffled speech". Without the caller telling him 'where' he was calling from, he couldn't have known WHERE the call came from. This proves that he MUST have been simply monitoring the open line and that he received NO call.