The Clown was angry. He had been played, and what made it sting worse was that he saw it coming. Or thought he did. When Kyrexiel brought Urlk for training, he suspected what was happening– that Kyrexiel wanted the boy to learn his network.
And he tried to limit that by only using him as an errand boy to send letters with no details. But the boy must have gotten a way to know who was sending and how he was sending the letters. Or read some of the letters himself.
Now someone has intercepted all his letters. Not only the one going out but the one coming as well. "It's been weeks and this is what I finally get? That we have lost contact with the Scion and we have no way to know where he is?"
The letters started flowing again. This means that Urlk must be far from anywhere to get information himself or try to block one.