Boooooo. Someone hasn't looked at the scoring system. 
Actually I was refering to the fact that although the game records that info for the mission log it does a really bad job of it in that
1) The data is wiped the instant the ship is actually destroyed (Which is pretty much the most obvious time when you'd want to use a SEXP to get at that information)
2) There isn't a SEXP to get at that information anyway.
Improving the way the game handles that is something I've been planning to add to 3.7 for a while (In fact I think we had a chat about it about a month back

).
So while you could possibly add something to the scoring system to make sure that it kept a log of which weapons had been used against a ship it would be pretty pointless unless you also made sure that information was also recorded after the ship was destroyed. Otherwise you'd get all kinds of false negatives because although ship X was hit by weapon Y it was also destroyed by it.