Okay, that clears it up a bit, but Ventus met Sora after Vanitas was defeated, right?
Yes. Basically what happened was that when Vanitas and Ventus fused, they created the X-Blade. So the X-Blade was connected to their hearts. When Ventus destroyed the X-Blade it damaged his heart and Vanitas got destroyed. Since Ven's heart was damaged again, it went back to Sora to be healed.