The solution would be to learn this button into your C7. But that doesn't answer the question you actually asked.
It's possible that Pioneer used another device ID in the code for that button; many devices use multiple device ID's to encompass all their functions. If Rob's around, he can probably tell you right off whether this device does or not.
If you know someone with a Pronto or a JP1 box, they could analyze this IR signal for you and tell you the protocol, device ID, and the function code (EFC) for this device/button.