The mystery has been solved.
Well, one of them at least.
The Falcons have announced that the prank call placed during the second night of the draft traces to defensive coordinator Jeff Ulbrich. In a statement, the Falcons said that Ulbrich’s 21-year-old son, Jax, “unintentionally came across the draft contact phone number” for Sanders. It was on an “open iPad” while Jax Ulbrich was visiting his parents’ home.
He wrote the number down with the plan to use it for a prank call. Per the Falcons, Jeff Ulbrich was not aware of the situation until after the call happened.