Microblink interview questions

I applied for a Tech Writer position and after almost a month received an email with a test assignment. I was asked to create a documentation plan for a new project. There were no screening calls or interviews beforehand, just a deadline for the assignment. After submitting my work to the hiring manager, I never received a response. Two weeks later, I followed up to ask for updates, but no one replied. I should have taken the time to research the company before investing my effort. I understand that the job market is tough these days, but this kind of behavior is unacceptable. I can’t escape the feeling that my work might have been used for the company's benefit, and that’s really disappointing.