This was a great deal, particularly to ORD where it was £12xx return in J and ~£200 more each way for First. Unfortunately it probably proved too popular with a lot of people in the UK taking advantage of the easy & cheap positioning to Inverness from Heathrow. The First deal was pulled a few weeks ago but I think the J price is still available for certain booking windows.
The price is helped by no UK Air Passenger Duty for flights originating in INV (£156) but this was only a small part of the fare difference compared to an LHR/MAN/EDI etc. departure.
I think you're probably falling victim to Google Flights relying on historical search prices for the initial results although there were reports of people still being able to ticket the F deal through OTA's (AmEx in particular) for a while after BA pulled the fare.