After fighting bravely for a few days, I finally gave in and called in sick to work. A full day of sleep had me feeling much better. I found out later that instead of calling in a teacher to replace me, NOVA had instead provided students with multimedia lessons taught by a teacher from another branch.
NOVA has their own video conference equipment available for multimedia lessons. This allows students to learn from home, or to get lessons at their branch in another language. There is a huge demand for English teachers in Japan, but a much smaller demand for French, German, and Italian. The most efficient way to provide this service throughout Japan is to have the non-English teachers based in Osaka (NOVA HQ) who can virtually commute around the country where they are needed.
When a teacher is not available in person, students generally prefer a MM lesson to rescheduling. However, they did tell me that it’s just not the same as physically being in the same room.