T0020. The Idiot's Calling Card

Nasruddin forgets to be at home for appointment. Angry man writes "Idiot!" on the wall of Nasruddin's house. When he meets Nasruddin later, Nasruddin says, "I saw your calling card."

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Notes:

Here's my short version:

Nasruddin’s neighbor came to Nasruddin’s house exactly at noon; they had agreed to meet to discuss an important matter. Nasruddin, however, was not there. The neighbor waited for a while. When Nasruddin did not arrive, he scrawled the word “IDIOT” on the wall and left.
He ran into Nasruddin a few days later, and Nasruddin said, “I apologize for not having been at home the other day.”
“How did you know I was there?” his neighbor asked.
“Don’t you remember?” said Nasruddin. “You left your calling card.”