HMRC have a national Options to Tax unit – their email address is [email protected] . If you explain the situation and quote his former VAT registration number, they’ll be able to check whether he ever notified them of an option to tax.
I still think it’s unlikely, given that he was charged VAT on the purchase and (unless he let any areas of the pub out to anyone else) I can’t think of any reason to opt later. But always worth checking…