Corrected entry: When Mordo and Dr. Strange are in the New York sanctum running from Kaecilius, Dr. Strange says that he stole Kaecilius' teleportation ring. But later on right before Kaecilius kills the Ancient One, he uses his teleportation ring to open a portal.
Mr. Bob
2nd Apr 2018
Correction: Just before the Ancient One came along, Kaecilius tackles Strange. We see him take the ring back.