KZLA LOS ANGELES A2832/10 - THE FOLLOWING RESTRICTIONS ARE REQUIRED DUE TO NAVAL AIR WARFARE CENTER WEAPONS DIVISION ACTIVATION OF W537. IN THE INTEREST OF SAFETY, ALL NON-PARTICIPATING PILOTS ARE ADVISED TO AVOID W537. IFR TRAFFIC UNDER ATC JURISDICTION SHOULD ANTICIPATE CLEARANCE AROUND W537 AND CAE 1176. CAE 1155 WILL NOT BE AVAILABLE FOR OCEANIC TRANSITION. CAE 1316 & CAE 1318 WILL NOT BE AVAILABLE FOR OCEANIC TRANSITION. CAE 1177 WILL BE AVAILABLE FOR OCEANIC TRANSITION. W537 ACTIVE, CAE 1176 CLOSED. SURFACE - FL390, 09 NOV 20:00 2010 UNTIL 10 NOV 01:00 2010. CREATED: 08 NOV 20:52 2010
NOTAM was supposed to start three hours after the plume was seen (reported as @ 17.00 Pacific).

Marc Ambinder, who is an encyclopedia of how the government works, thinks it could be a a spy satellite. He tweets: When launching spy satellites, opsec = timing of launch... post-launch cover story can be weak.
So, basically, it could have been an impromptu satellite launch.
http://www.businessinsider.com/was-t...#ixzz14tGttNAf