Is it possible that a ct scan would miss the fact i may have had an ovarian cyst rupture?

Yes: A ct "slices" (reconstructs actually) into 1-2cm thick windows. So many cysts disappear into the resolution limits of the test. Also, some fluid can be normal, so ct may not identify problematic fluid from normal fluid until greater volume present. Ultrasound is the best test for this.

Yes: Ct resolution has gotten better and better, and a ct scan with IV contrast can usually identify even small ovarian cysts. But if the ovarian cyst ruptures, the ovary usually looks fairly normal on ct. If it was a small cyst that ruptured, the amount of fluid in the pelvis may overlap with normal physiologic fluid. Only if the cyst was large and/or bleeding would the ct likely be diagnostic.