Why did the professor ask other students about my absence even though he already knew about my sickness?

About 1 hour before the lesson I mailed the professor informing him about my sickness and that I wouldn’t attend class that day and that I would later send him a medical note. He replied within 2 minutes and told me not to worry About it. Later that day a fellow student texted me that the professor asked other students about me. But why? I know he is only teaching one class this semester.

Why did the professor ask other students about my absence even though he already knew about my sickness?
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