He does - he says "Even information about those creatures erases itself over time".
I thought so.
Given that they were still using Amy's photo of one several months later, I'm pretty sure they meant knowledge rather than information. That is, anything written/stored/etc. is retained, but anything memorized eventually fades. Given the context of that scene and the way it was explained to Canton, that's the only thing that makes sense.
The orphanage caretaker, however, did demonstrate how even written data might be erased; by cleaning it up thinking someone else had put it there.
Not necessarily, yes, they were using the photo to make the hologram but we don't know the shelf life of the data is. Of course we don't know what was going on in the orphanage, how long that had been there, if it was the caretaker writing it, who he was talking to, who the woman in the door was and various other things, so that might have been someone else trying to tell him to get out and the post hypnotic suggestion was telling him to clean it off.