I think where their attention is and therefore what gets encoded is similar to the rest of us. In one instance they were unable to recall what the interviewers were wearing after spending two hours with them. They remember their experiences visually, essentially. So if information was not actually recorded, it can't be searched for.

On a different note, I'm curious how long people with photographic memory store the info at the same fidelity. Does their perfect recollection of a landscape they looked at for a few minutes fade somewhat after a year or so?