Meta Software Engineer interview questions

Recruiter contacted me through LinkedIn. Set up a ~15min call with the recruiter a few days later. Recruiter asked me about my current job and project. Everything went well and I was set up for a technical phone screening with one of their engineers. We set up the phone screening two weeks out. Facebook engineer called me in two weeks and asked me about my current project, then jumped straight to the coding challenge. (See below to read about the challenge). I got nervous and did not complete the challenge. At the end I got to ask the engineer a few questions about Facebook. Two days later I got a nice rejection email from the recruiter.

Technical interview on the phone with a software engineer. We went through two questions and I thought it went well, but did not get an offer. I wish they let me know why they rejected me