Plame's Name: Was it Cheney or a State Department Official?

I'm having trouble reconciling this sentence from a WashPost piece on the Plame case:

According to the indictment, Libby learned Plame's identity from a senior State Department official in June 2003 and was told by Cheney that she worked in the CIA's Counterproliferation Division.

With this one:

Although the focus has been on Rove and Libby, Cheney himself has been publicly implicated in recent days in the chain of events that led to the exposure of Plame. The New York Times reported Monday that Fitzgerald possesses notes taken by Libby showing that he learned about Plame from the vice president [on June 12, 2003] a month before she was identified by Novak. The White House did not dispute the report.

Where did Libby first hear of Plame? From a State Department official or from Dick Cheney? What difference does it make? Maybe none, but one thing doesn't make sense in all this: Libby evidently lied to try to protect Cheney, by saying he had learned of Plame's identity from journalists. Why didn't he just say he was first told by a State Department official? Wouldn't that have mitigated Cheney's risk in being involved?