There was one item left in stock and it was a legacy shop. It brought up an error like "the purchase failed; the shop may be out of stock" but it is there. I tested it and the error happens with new and old shops with more in stock as well.

The text on the move button changes to "buy" afterwards.

(Love the new search page though!)

[edit] I'm guessing Reya's right and the bug is that

1. "move" from shop search doesn't display informative error message if inventory is full
2. "move" text from shop search turns to "buy" after first click

Ohh that must have been it! (It's working now in any case)