Bandages tend to digest easily enough, so it may just take a few days to go though his digestive track. Based on the amount of time that has passed the only way to get it out is to wait and see if it passes or for the vet to go in and retrieve it.
Since this is not a large item I would recommend waiting and watching the stools. You will want to keep a eye on him and if he displays any signs of a blockage then he will need to see his vet asap. When a pet has a blockage, they may exhibit any of the following symptoms: vomiting, loss of appetite, distended belly, an absence of feces or a change in the feces, blood in the stool or vomit, drooling, and retching or trying to vomit with the meal coming up or nothing coming up. If your pet exhibits one or more of these signs a trip to the vet is highly recommended.Walter