Claudius
I don't think their claim should have been a penalty, either, even if it was by the letter of the law. It would have been against the sprit of the game to penalise someone for making, and I've been trying to find the right word to describe this, an insignificant mistake. Gabriel clearly was just repositioning the ball to restart the game.
It was a bit like when van Persie got sent off against Barcelona, even if the ref could argue that he kicked the ball a few seconds after the whistle blew, it was an unsporting decision and there was no reason why the ref couldn't have been lenient in the position.
It would have been the same here, and had the situation been reversed, I genuinely wouldn't have even noticed that happened, much like very few did in this game until after it was all over social media.