Seven Card Monte

<spoiler>The sky-writing clue is 263- [1], which suggests a phone number. Rather than the numbers on the cards, one pip on each card is clickable and turns the card over. If you index the pips:
1 2 3
4 5 6
7 8 9

... the clickable ones are in positions 8, 7, 7, 4, 7, 8, 6.

Calling (877) 263-4786 gives the following message:

"OK, I am officially impressed! Good job finding me. To solve this puzzle, listen carefully and tell me what disappeared on Halloween, 1926 at 1:26 p.m., Room 401, Detroit."

The answer is: HOUDINI (who died at that time and place)</spoiler>

To next puzzle: Postcards.