Patrick seeing the kiss between Sabrina and Carlos could have gone either way. It could gone where Patrick realized that Sabrina had someone else and he could be with Robin again. Or Patrick sees them kissing and realizes how Sabrina felt when she had to watch him kiss Robin. TWICE!!! That sick-to-your-stomach feeling of seeing the person that you were supposed to be married to and totally in love with kissing the person that used to be all about and totally and completely in love with.
The way Patrick pulled Carlos away from Sabrina, he was acting like they were together, like nothing had changed; the way he told Carlos to stay away from Sabrina.
It was totally obvious that he is still completely in love with Sabrina.