I guess consider yourself lucky it didn't hit you or another more expensive part of your bike and causing you to get knocked off the bike, etc.
It must have been one heck of a hit like you said to knock off the side cover since those 3 tabs are pretty firmly snapped on if you ask me.
the side cover probably would not be any good anyways flying off even if it did not get hit by another vehicle.
try looking on the bright side I guess, could have been much, much worse.

I went for a ride today as well but on my scooter instead since saw the rain clouds a coming in. Got wet on the way to the next town so decided to turn around and head home since the winds were pretty severe at 20+ mph gusting to 30 mph at times. It handles the wind pretty well for 350lbs. vs. 800lb Valk but at least with the Valk, the fairing gets the brunt of the wind vs. my body getting pushed around on the scooter taking the brunt of the force whipping me around like a wet noodle at 60 mph.