Quote Originally Posted by Throbert McGee View Post
I'm pretty sure that "куда ты ходил?" by itself can be understood as referring to a single trip there and back -- because a round-trip is, by definition, not in one direction only!

But "куда ты сходил/съездил?" serves to emphasize clearly and definitely that there was just ONE trip there and back, avoiding the ambiguity of the non-prefixed form.
Yes I agree with this.