He gave it to them
Probably to be able to leave the airport! And his wife was held separately!
This is pretty incredible action even for the USSA
He says they never even asked him to testify
A draconian airport detention and subpoena was pure jackboot intimidation
Now begins the mueller process of bankrupting him with legal fees until they can find something he pleads guilty to!
Yes, its common procedure to separate people to see if their stories contradict. FBI/ICE can confiscate their phones (when it happened to me, I wasn't presented with a choice) but unless a judge gives them a warrant, any evidence is not admissible. They can't detain this person unless he is officially under arrest or charged with a crime.