Having looked through the synonymous for researcher and come across the following definition of an investigator as a:
person who checks thoroughly
is there a word, or phrase that describes
a person who checks rapidly
without implying sloppiness or inaccuracy.
A Librarian.
This answer is half joke, but only half. Anybody whose ever gone to a Librarian with a question can tell you a good story or two about them coming back with a good answer in an astonishingly small amount of time. Knowing where to look for just about any information at all is these folks' calling, and they tend to be amazingly good at it.
How about just an efficient researcher? If you want something a little more artful, you could use the phrase human search engine.
Resourceful - Capable or clever; able to put available resources to efficient or ingenious use; using materials at hand wisely or efficiently.
Chances are, they have google-fu.
That dude's a whiz at numbers research, a regular math maven.
Oddly enough, Urban Dictionary looks to have a better def for whiz than Webster online. 'Whiz' might be a little slangy, but it's been around nearly a hundred years now.
I cannot think of a single word for this. However, you could say he or she is an efficient investigator. Efficient is defined as:
Functioning or producing effectively and with the least waste of effort; competent
Or he or she is a capable investigator. Capable is defined as:
Having the ability required for a specific task or accomplishment; qualified
