No, not a gap. The ball would be dead, all right, but nothing in the NFL rule stops the action of a dead ball, or of a player while the ball is dead, from being used as evidence of prior possession. A kicked ball is dead on contact with part of the goal, but its subsequent motion still has to be watched to determine whether a goal is scored.

But if I were reviewing, I wouldn't consider what's shown here to be convincing enough to overturn a field call.

Thank you for clarifying the rule for me.

My determination is that touchback was ultimately the incorrect call because even if he fumbled prior to his contacting out of bounds, he retouched the ball while clearly out of bound and prior to the ball contacting the pylon, which kills the play. Unless I misunderstood Robert Goodman's post and the gap I mentioned does exist.