Amazon phone screen skipped second case?

I had a technical phone screen for a data scientist position recently at Amazon. I got pretty nervous, locked up, and felt like I didn't answer the first case question very thoroughly. The interviewer said there was a second question but we could just skip it, then we went through the behavioral questions. Then they let me ask questions and we hung up. Why would they skip the second case question? Is it because I didn't do well enough on the first one?