This article makes the claim "It's impossible to recover images with perfect accuracy. The myth of photographic memory". That is interesting and I wonder if it works the same way for images with text on them or not. While the article does not acknowledge photographic memory, it says that memory that comes very close is "eidetic memory". Good eidetic memory is something people are born with, it can not be learned. After staring at a picture for 30 seconds, people with a good sense of eidetic memory can remember the image with very great detail. Still, even for seasoned eidetikers, their reports may contain flaws and the vivid memory only lasts a few minutes. Children have a very good eidetic memory that seems to fade over time. This might explain why children have a very keen sense for detail.
So, was my teacher a fraud? Well I'd like to hope not. I bought into it. Maybe she never lost her "eidetic memory" that she had as a child. I think it'd be very interesting to get inside her mind.