Look, I'm not saying he definitely had it, but speaking from experience, I didn't know I had it either until I showed positive for antibodies. I felt a little under the weather for the first week or so, then it went from nothing to "My dad caught me getting fingered in my room by my crush" grounded in a day. Couldn't get the energy to leave the bed, winded if I walked to the next room, feeling like I was gonna die. It is VERY possible, and fits the information and timing that he though he had the sniffles, took a few days off, and by the time he realized he was in trouble was in over his head and was thinking about mortality instead of updating a Patreon. Everything from his post seems to me like things spiraled out of control fast, and that's what it did to me, so take it or leave it.
I'm just saying if you want to give up on it, there's nothing that I can say to change your mind, but there are other possibilities than him abandoning it.