In any emergency operation, the surgeon had no way to guarantee you that you would not lose both tube and ovary and I doubt he did assure you that under no circumstance would he remove the ovary. A rupture of an ectopic pregnancy is a life-threatening emergency. If rupture had occurred, the ovary may have been destroyed in the process.
try to obtain and see the surgeon's report of his findings. any specimens sent for analysis will define his decision to remove the ovary.