Throw-in Spot

[Steverz]

Would someone please show "exactly" where in the Rule or Caseplay book the answer to this simple question that our association started throwing around.

Caseplay: Along the endline in the backcourt, A1 inbounds the ball. No other players are paying attention and the ball eventually rolls out-of-bounds along the sideline without ever being touched. Where does Team B have the ball for a throw-in?

They are saying the throw-in is where the ball went out-of-bounds, not where it was originally inbounded even though no player touched the ball. Which is it since I can't seem to locate it in the books?

Thanks