How long does it take a doge trc's digestive tract to pass an object?

My 7 month old Boxer just ate the legs off my daughters Barbie doll (from the knee down). I am assuming he swallowed the legs because I can't find them anywhere! He ate it about 8 hours ago and has urinated, passed some stool (and I did see a small piece of the doll come out), eaten and been playing steadily since. How long should I watch him for signs of a problem?