My firend stole 4 of my amiibos UPDATE 1.0

[Mr_No]

I'd suggest to confront him, but without any hostility. Try not to say "I need to talk to you" or anything like that beforehand, or else he'll be preparing or remembering excuses for that moment. When confronted, the gestures he makes with his face and body will be a clear indicator if he's hiding something.