I am not an expert, but like you, I have a dog who will put anything in his mouth and swallow. If it has been about five days with no signs of pain or trouble, then I think you might have gotten a lucky break. I'm pretty sure problematic signs would have made themselves apparent by now. My experience with my dog (who has been to the vet before for ingesting foreign objects) is that he generally showed signs the same day or the day after that he had eaten something. Bones, especially fragmented ones could get lodged somewhere in there so keep him on watch, but I think you might have avoided a costly trip to the vet. Best of luck with the pup.