Looking at the box score, it looks like this happened in the middle of the 1st quarter. When it comes to handling the clocks, would everyone agree with this?
Since this one happened before either of the two-minute timeouts....
Ideally, the entire crew, and the game clock operator, all recognize that what happened was a fumble (on fourth down) and no touchdown signal would be given. So the game clock would continue to run when the ball is dead.
The play clock would be set to 40 and start. And it would be set to 40 regardless of any confusion because it goes to 40 both because the play is dead or even if the play clock operator thinks it's a touchdown.
Thinking they've scored, Team A players will probably be celebrating some. Officials will be getting the ball to set it back to the B2. If the play clock is below 25 when the ball is spotted it would be pumped back to 25.
But if it's after the two-minute timeout in either half, the only difference would be that the game clock should be stopped when the ball is dead due to the Team A first down. And then restarted on the Referee's signal.
That's the ideal, but you probably have to deal with a celebration and getting it communicated to everybody on what will happen next. So it seems that lots of crew awareness would be needed on this one about the game clock and play clock. Especially, if it was late in a close game. And if there's a crew discussion needed, obviously the clock could be stopped for that.