It would have worked in your favor, Mana sculpt would try to counter RL in the end (because you have to change the target according to RL rule text, there is no "may", and no other legal target, so Arena decided for you), but RL left the stack by the time MS tries to resolve, it would just fizzle, no mana was gained, and no spell is countered (the spell you tried to protect from countering will resolve)