Though I agree with you that placing a 911 call simply because somebody failed to show up for work is odd in the general sense, this particular person was a medical doctor with scheduled patients. Thus, his failure to show up was more than just "not in his character".
As another poster mentioned, doctors always call when they cant come in for scheduled patients. This probably extends to air line pilots as well. I imagine that some may give uhhmm..... spun explanations ala:
"Hello, I cant come in today. (Coming off a three day bender- Yikes- no, I cant say that). I uhmm..... think I might (key word) have Covid.- showing multiple symptoms- especially the nausea and soreness (Imagine that)".
But, they always call.