How did Baha get the body to became permanently ethereal in the first place?
By literately carrying the corpse into the Ethereal Plane and leaving it there.
Interplaner travel is available at the 9th level through Plane Shift (cleric 5th) or
Shadow Walk (bard 5th) (shadow & ethereal don't link)
and it just gets easier as you level. Your Shadow-Creature Template/Class even grants interplanar travel as early as ECL 2 by using the Plane of Shadow as a pit stop over two days and Badly has been a Shadow-Creature Ghost every since he was made for the stealth benefit so if unknown at the time corpse thing is a problem it can be easily remedied. Also he now looks like Freddy Kruger for the moment until I can find a better image.
There is also the campaign alternative of simply using portals. The optional Deep section of the Ethereal Plane has tapestries that connect to every Plane and you can find a specific tapestry in 1d10x100 hours. On average a Ghost can find a new portal to the Material Plane once every 23 days. It's just a matter of getting to the portal's location on the Material Plane. The catch is, if the portal is two-way it's also likely useful and either guarded or a mini-sigil. Which also makes it a great place to consider hiding Espers away form the AA *wink wink*
Edit - Made a huge up-till-2am pass on the NPCs. They now have bio/quark entries!
Kenny: finally getting around to adding his feats, do the crafting feats affect WBL?
Kenny's Homunculus: mostly detailed out now.
Baldy: added the warlock level and adjusted skills, reason for ghosting added, still of a ton of gold left over to buy stuff.
Lumpy: the 2nd level nymph joke is now a full fledged 4th level follower! She can handle food/water, murder people in snow, sell drugs, and run an election campaign better than Trump.
Bulbasaur: So I ran with a Spellwurm trick using Psychic Reformation to restat it and Mindstealer so it can eat memories as a new Plan B contingency in case future kidnappings are not so complaint. Probably a little iffy, I didn't go as far as using Mindstealer to acquire abilities so that's probably not an issue, buffing Spells were traded out for stuff that does things for you while you lay around so I doubt that'd be an issue too, and I have a 4th level follower slot I can toss the concept into using a custom built Sorcerer to pretty much do the same exact thing, but idk. I did it using MoE's 8k buyable helper because I've never followed through on the trick before and I could see other people saying they want one too which could probably lead to the dark side of the force. If I need to revamp Bulba into "Boney" I can.