I suspect, although I don't know of anyone doing this myself, that there are people doing this all the time, just as a hobby or for the hell of it. The equipment required is minimal and so are the storage requirements, so you could easily log everything. Even in 2001 it wouldn't have been cost-prohibitive.

There are probably people sitting on years worth of data, just because that's a hobby for them. 9/11 is probably one of the only dates that's of interest to the general public.