schiff wants whatever it is so he can leak it..how does he know about it if he was not in on its origination?
Not sure what you mean about "origination," but the IG for the IC informed Schiff that the compliant exited.
What seems to have happened next is that inspector general Atkinson decided to tell the congressional committees about it himself: he wrote a letter to both the House and Senate Intelligence committees telling them about the whistleblower complaint's existence. It's unclear how many details Atkinson gave, but he evidently did not include the full complaint.