The Maurauder's Map in CoF

[adatole]

No: HPFGUIDX 36139

With all the conversation regarding the Maurauder's map in PoA, I 
wonder why Fred and George didn't use it during the CoF events?

They could have spotted Ginny going around on her own.

They could have spotted a dot on the map (in the pipes) 
marked "Basilisk".

For that matter, in SS/PS, they could easily have found out what was 
3rd floor classroom (BIG dot marked "fluffy").

I realize that this would require them to be looking at the map at 
key times (Almost everyone was struck when the rest of the school was 
someplace else - at the Halloween Party, at the Quidditch match, 
etc). 

But it's just a thought. 
Leon