What would you do?

[gumpire]

Well, I don't see the relevance of what rules the games is played under.
Basic umpiring ethics require that you call the game and put forth best effort to call it correctly.
If you clearly saw the call made by your partner was wrong, you have an obligation as an official of the game to discuss with him at that time. If this were a regional or state tournement and team B lost because of the bad call that was not discussed between the officials, I think you'd have bigger concerns than whether or not the FED rules specifically state you should discuss it.
Use your common sense when your umping a game...a bad call should be addressed immediately. I'm not saying the call should change, only that you let what you saw as a bad call stand, and did nothing.
FYI I found the same wording in several rule books (i.e., NCAA (Rule 3 Sect. 6(h)), IBAF (Rule 9.04(3(b(c))))), so I'm sure that it applys in some way to yours too.

Hope this helps!