Actually, there is. All you would need to do is install what would amount to a laser pointer in the center of each upright, aligned to point straight up. Connect it to a relay to signal the booth, and perhaps a green light at the top of each upright. When (if) the ball passes through the beam of light, the signal is activated showing proof positive that the attempt was good.
The costs would be minimal, and it would work in both indoor and outdoor stadiums. You could even have a cap like the ones on top of semi-truck exhausts to keep the lights clear of snow, sleet, etc, and have it linked to open when the nets are raised behind the goalposts.
Again, a viable, easy to design and install system that would be of minimal costs and be proof positive of the outcome of any PAT or FG attempt.
V/R