it wasnt a pen but not for the reason you said. had the keeper tripped him without touching the ball it would've been a pen, even if keepers intentions were getting the ball like everyone expects of him.
the fall was inevitable, i know, that part wasn't a dive, but he still did some awkward motion at the end of the fall and asked for a pen. diving runs deep in his veins.
UNLESS we cash in on neymar and sign one of hazard/reus/griezmann or maybe some other crazy good left winger :DD ney ney can fk off if he doesnt bring harmony to barca