Quick update, received a reply to our complaint. 5K avios for myself and 5K for companion on the same booking. "We’re very sorry you weren't served correctly on your flight to Bucharest recently. This isn’t what the usual service is on our flights and we understand why you needed to let us know." "I have sent your feedback onto the relevant team who will investigate this accordingly."

Satisfied with the response and outcome. The mystery on what actually happened will remain.