Pick a card, any card

I was playing with cards, as I often do, when Zach walked up.

“Can you do a trick for me?”

“Sure,” I said. I like doing them.

As part of the trick, I asked Zach to pick a card, any card, and remember it. After he did, I collected a bunch of piles of cards, his card included in the piles, and then placed each card face up in columns.

“Now,” I said, “which line is your card in?”

He looked for a few seconds.

I watched for a few seconds more. “Do you see your card?”

He nodded.

“Well, which line is it in?”

He looked at me again. “Well, it’s kind of in two piles. There’s a five here… and a five here…”