There is no such thing as magic. Magicians just do stuff that they know how to do and refuse to tell anybody how to do it.
If I knew how to set the central heating but nobody else in the house did, I would tell them. I wouldn't get all fucking mystical about it, put on a funny hat, get a lady in sparkly swimming costume to stand next to me, refuse to tell anybody else how to do it and claim I was a central heating magician. That is exactly how magicians operate when they pretend to pull a playing card out somebody's anus or whatever! It's annoying and rude.
They should do the trick, explain how it was done, apologise, then go home.