You can add bar of soap to the list of things that Bob has eaten. I found him chewing on a little lump of soap the other night at bedtime and I had to pry it from his jaws. He just doesn't want to give his little treasures up. He must have stashed the rest of the bar somewhere because last night DH found half a bar of soap under his pillow. Bob likes to sneak up to our room and sleep on our bed when I forget to shut the door. So one half plus a little lump saved means about 1/3 of a bar of soap is in Bob's digestive system.
Maybe that explains the belching. I never knew dogs could burp, but Bob can.