How about

1. Brief your boss what the problem is, apparently, it's missing the launch milestone.  

2. Show your boss the specific impacts to you and your organization.

3. Tell your boss how you plan to address the issue.  Recommend a specific approach, along with alternatives, pros and cons for each approach, and why you recommend that specific option. 

4. If needed, accept responsibility for the outcome.

5. Have a lessons learned meeting upon completion.