The circumstantial evidence jumps out at you. Yet the more likely scenario is that he was met by a CIA agent who set him up to be the fall guy. That meant getting him his job and seeing to it he would be in the right place at the right time. His weak presentation at the Cuban embassy sounds a lot like a mark following up on false instructions as well. Presume he was targeted, misled and made part of a false story line in order to set him up for his job.
It was enough to get him securely in the building in question. He was never meant to live to testify.
Needless to say this meant that curiosity over Mexico was thwarted by the CIA and they did just that as this makes very clear..