He was a collector of THINGS but not necessarily the knowledge associated with them
since he collected secretly he didn't travel in the same circles that knew the Doctor and having captured a dying Dalek, it was just another thing for his collection so while he had on he didn't really know what he had
- Amy Pond in "Victory of the Daleks" revealed she didn't know what a Dalek was - which was commented on as unusual by the Doctor. Perhaps something happens to make people forget by 2010.
It's also possible that Amy is not actually from 2010, or that she's from some sort of alternate 2010, or that she was living inside some kind of temporal anomaly. Her boyfriend Rory had an ID badge that was issued in 1990, but if "The Eleventh Doctor" actually took place in 2010, Rory, who appears to be only about 20 years old, would be too young to have such an ID.- the badge was a production error not a future plot point.
- Also, as the Doctor keeps telling his new companions, time lines can be overwritten. So the events the Doctor witnessed while with Henry van Stratten could now not happen because of all the Dalek invasions.
The event might have been removed from history, meaning there was no Dalek invasion.