Was this a simulated miss? You can't fire live missiles at other aircraft during mock combat.
You don’t waste a live missile to simulate a miss, and you don’t carry live munitions during DACT.
We need to remember that these are entertainment programmes first and foremost, so often editors will splice in unrelated footage just to spice things up a little or to make up the numbers if they didn’t get enough/any actual footage from the event they are reporting on.
Also, looking at the footage again, that is definitely a gun track and not a missile lock (you will get a box/circle around the target with a missile lock), the trail is just the computer projected trail of where your shells will be by the time it reached the distance the enemy plane is if you pulled the trigger. Something you will only see with a gun track.