Another tip: if Haven (note: try thinking up a name instead of using a noun like that) was alone with Buizel on the island and does ever end up getting back to civilization, maybe use that sepeartion from other people to highlight just how far he had strayed from humanity itself. For example, if he's being interrogated by the police or something, make everyone else hear his talking as slurred and difficult to comprehend, from not hearing anyone else's voice for so long.
...I've got no idea where that came from. It's an ineresting premise, but like Feign said, try to pull a twist on it. For example, he could have crash-landed into a... meteor with a Deoxys in it or something and now he has to stop Deoxys from... bringing down the moon or... something. xD Get the idea?