Swallow Whole and changing dimensions

[Dafydd]

So if you are swallowed whole by some outsider, and someone uses dismissal or something similar do you get out of tummy free?

What happens if the thing that ate you decided to leave the local and plane shifts (or similar ability) of its own accord? Can it bring it's doggy bag?

Both these assume the swallowed whole person is still alive. Dead, I would assume your body gets a trip the multiverse.

[That Crazy Alchemist]

I interpret it the same way you are. Its the same reason a Summoned creature cant pick up an object, then get de-summoned and now that object is lost in the aether. The item just drops to the floor is all. As with a de-summoned creature, Dismissal merely sends whatever is not native to this plane back where it came from, contents of its stomach and anything else the outsider did not bring with it to the Material Plane, alive or dead, would rather disgustingly stay behind.

Now Plane Shift is a different story since that specifically allows you to voluntarily take people with you. Anyone living inside its stomach would get a save, but any item or dead thing will go with it.