Not being in EE, I didn't know that this was possible
Not only is it possible, it has led to many interesting failure modes in the past since visible light doesn't usually erase an EPROM, but sometimes just flips a few bits. The n00b complaint, "it works fine until I turn on my desk lamp" used to be a pretty common one in EE labs and online help forums :-)
I don't buy it for a minute. You can leave an uncovered EPROM in direct sunlight for a week, and the data will probably survive.
I'd suspect a localized "EMP" transient from the camera flash before I'd suspect an erased EPROM. It takes a lot of energy, in the E=hv sense, to erase an EPROM.
Believe it: windowed EPROMS have been used as cameras. Their light sensitivity is legend.
[edit] actually I was wrong about that. The memory devices used as cameras were delidded RAMs, not EPROM. EPROMs are light sensitive, but too slow for that.
Not only is it possible, it has led to many interesting failure modes in the past since visible light doesn't usually erase an EPROM, but sometimes just flips a few bits. The n00b complaint, "it works fine until I turn on my desk lamp" used to be a pretty common one in EE labs and online help forums :-)