Hi and welcome!
Sorry to hear you are going through this. Lows like that really knock the stuffing out of you.
Yes, I have seen rapid fluctuations from OK, to very low, back to OK again on my Freestyle Libre screen, so yes, it is perfectly possible. And it makes it very difficult to know whether it is REALLY a hypo, or not, because if you miss that 2 minute window of being at the low point, then no one believes you - least of all yourself!
The reason the blood glucose can rise so quickly, and leave us feeling so bad, is because when the body detects the sudden drop in blood glucose, it goes into panic mode and puts your endocrine (hormone system) onto High Alert. This dumps a massive amount of stress hormones like adrenalin and cortisol into the body, which has the effect of suddenly raiding all the glucose stores your body has in the liver and the big muscles. These enter the blood stream very quickly to correct the low. Literally within a very short time.
However, because nothing is free we then have all those stress hormones that need dealing with too - along with the 'feeling like we've been run over by a bus'. I think that zonked feeling is more to do with the stress hormones than it is to do with the blood glucose.
Hope you feel better soon, and get over your virus. My blood glucose is always much more unstable when I have an infection or illness, and food poisoning has been the worst so far.
Take it easy. It can take a couple of days after a hypo like that before we feel right again.
If your symptoms have returned in the last two months, have you changed eating habits? Or had this bug for long?
If not, I would make an appointment and ask for a checkup. Hopefully they will bring your next scan forward.