A super bummer, but not so weird. Sickly dogs always come into veterinary facilities (obviously), and the kennel cough vaccines only cover a small portion of the different strains.
Teeny had kennel cough last summer . . . maybe fall, can't remember. Either way, she had been vaccinated for it. My other dog, who she shares a water bowl with and who's mouth she licks incessantly (and no I didn't separate them during the week she was sick), and who ISN'T vaccinated for it never developed it.
It's like a cold. It happens. I gave Robitussin gel tabs twice a day for 5 days, and gave slippery elm three times a day for 10. But within 7 days it was gone.