I see stories that claim that it was an aircraft contrail and other experts claiming that it was a missile. I haven’t followed it as meticulously as I could have but hadn’t heard a definitive determination had been made.
The folks at Contrail Science did a Yeoman’s job of putting things into perspective.
http://contrailscience.com/a-problem-of-perspective-in-the-oc-new-years-eve-contrail/