I didn't catch how old, Tovah, just 20 yrs older than you. Certainly as people age, and especially if they're not well or strong and fit, they can more easily lose cogency when physically stressed. My Dad made it to 98, generally amazingly sharp until the end, but he had 4 or 5 episodes of transitory dementia (my phrase) scattered through his last decade. The first time it was a reaction to synthetic narcotic painkiller drugs (maybe Vicodin), another time it was a bad sinus infection that made him nuts. Most of the times, he didn't slow down much mentally (which would have been easier on us!), he just saw things that weren't there and believed things that weren't true. Often he'd wake up from a dream, and nobody could convince him that the dream was a dream. (Dad was used to being one of the sharpest people in the room, so he'd carry on these conversations the way he'd taught us how to argue logically when we were kids: "OK, let's assume for the sake of argument that you're right, and we're NOT in China. Then how do you explain. . ." It was exhausting, and occasionally hilarious, but also occasionally nasty and divisive.)
Each time, it resolved itself completely in a few days, either when we identified (and discontinued) the offending drug, or when the infection was cleared up. Interestingly (and not surprisingly, if you think about it), his false "experiences" didn't get erased when his brain functions recovered. We just tried not to talk about his trip to China(!).
For any of us, that kind of "losing it" can be one of the most distressing and upsetting things that we've ever experienced, and it can be terrible for the patient's family, too. Do get answers and insist on good care, but also try to do your best to respond with as much patience and love as you can muster. And don't sacrifice your own needs (like sleeping and eating and even recreation), either!