I can't see where the ball ever hits the ground... it looks like it is loose as they are both going to the ground, but after the runner's knee hits; and, when Butler rolls up the ball is on his arm or left side of this body, something... and his momentum flips the ball into the air - it wasn't the ground that caused the ball to jump up, it was Butlers rolling momentum.
I stopped it and tried to roll thru it frame by frame - which is impossible due to the poor technology and only 2 angles - I agree, in today's NFL we would have had 36 camera angles on it.
In the end, I don't see where it hits the ground at all though - if it's a completion, which is what I think they ruled, then it should have been down by contact. If it is not a completion, absent evidence that it hit the ground, it is an interception.
What it ended up being was a catch and fumble - when IMO, it should have been a catch and down by contact. Today's rules, I think it would have been an interception.
At the time, I remember thinking it was a fumble though, lol...