Wrong player steps in to take free throws

[Nevadaref]

You could have justified the T as unsporting behavior, however it was probably better to just switch the players since there weren't any FTs attempted.

You can T up your partner for not helping after the game if you wish.

[jdw3018]

I agree with Nevada, with the addition that a quick word to not try it again with the player who stepped in to take them may be in order.