Police say an X-ray of the woman's stomach showed the ring was there.
Investigators say 29-year-old Bryan Ford had been examining a ring worth several thousand dollars at a Zales jewelry store on Friday night in Orem, about 45 miles south of Salt Lake City, when he allegedly left with it.
Police say he was chased by an employee as he got into a car driven away by Schlegel.
Police say they were baffled as to the ring's whereabouts until the X-ray of Schlegel's stomach was taken.
Officers stopped the car and arrested both suspects a short time later.