Hello & welcome, I am Dr. B, a licensed veterinarian and I would like to help you today. I do apologize that your question was not answered before. Different experts come online at various times; I just came online, read about your situation, and wanted to help.
Now this is a situation where we need to tread with great care. If the bone is caught and pulled to firmly, it could cause damage to the colon/rectal tissue. In this case, instead of giving digestible oils and milk, you should be giving fiber (ie canned pumpkin, all bran) +/- non-digestible GI lubricants (ie cat hair ball treatment, lactulose, miralax). The former will help push the bone through if it can be and the other will ease passage.
Otherwise, if it is caught and Elliott is distressed or painful with this, the safest next step would be to have his local vet sedate him so the bone shard can safely be removed. At the same time, you can also have them xray him if any more shards are potentially lurking in the GI that may need removing.
Overall, its good that the bone got this far but this is a precarious situation still. Therefore, if he is comfortable, the above additives to his food could help him pass the bone. Otherwise, removal under sedation is the safest option to ensure he doesn't suffer any gut damage from this.
Please take care,