Emil was pretty cooperative and made a good job hiding how scared he really felt. He only talked about his super strength/durability, because these are the only things they actually noticed during the Wise Snake thing. He didn’t mention magical music and he didn't show them his horn (unless they asked him to take off his hat. then he said the truth - he has no idea what it means).

He didn't mention the names of the people he was spotted with, saying he didn't know them before and that there wasn't exactly time for introductions, what with the giant ramapging snake and everything. If they concealed their identity, he didn't give anything that might help the FBI find them.