Do you have plenty of substrate in the cage
Assuming you have the same hamster mix and it's an ok one, I would try scatter feeding it as well as putting it in his bowl - so the usual amount in his bowl and scatter feed about half a tablespoon as well on the substrate. That should encourage him to forage for the scattered food. Also are you changing the food in the bowl? If it sits there for a day or 2 they often ignore it but if you put fresh out they seem to go for it more
He probably does have a hoard somewhere - they often have more than one nest so they can hide more than one hoard, if they're worried one might be stolen!
Cleaning out too much can cause strange behaviours too. With a cage the size of the Barney and plenty of substrate in it you only need to do a substrate clean every 2 to 3 months and can just spot clean in between (if your hamster uses a litter tray there isn't even much spot cleaning necessary).
I have the Barney cage and it goes at least 3 months using a litter tray
You can do the wheel or toys as and when needed - it's better not to clean everything at the same time as it stresses them.
Also (sorry if you already know this) they are particularly fussy about their nest and hoard so that shouldn't be removed during cleaning - unless it's pee'd on. Then try and leave a bit of the old nest or hoard and put new food back in exactly the same place. Plus a new big pile of torn up strips of plain white toilet paper for making a new nest or rebuilding the old one.
After a cage move it helps them settle not to clean anything at the time of moving over, and not to clean anything for the first two weeks after settling in. If you've done either of these it may just take longer for the settling in and habits to form.