So here's a weird thing I found.

I'm able to list element changing candy on my shop.

The autosearch recognizes it.

But searching brings up nothing.

Put a shop terminal/counter in your room and see if it lists your light candy from there. Because on Ship 3, there's only one person selling Light Candy:

And searching for an item I have up for sale won't show my listing unless I view it on my Shop Counter.

So in short, the personal shop search won't show your own listings.