It’s hard to know generally, but in this case I think the fare was more widely known.

It was sent to 92,000 people who subscribe to “Dan’s deals”.

https://www.dansdeals.com/airfare-de...57-round-trip/

As another datapoint if helpful, I took the step of calling BA to find out what was going on, as the OTA are saying call Tuesday. BA confirmed it was a manifest error and all flights will be/ have been voided, but they will offer a 100 gbp voucher to all affected as goodwill (details were scant , I don’t know whether that’s per trip or per person, how the voucher will be redeemable etc).