The Trading Post took 750 currency but I got no item? Anyone else?

According to Blizzard support via this post, They can tell if you still have the tender in your inventory and that its a display issue.

if this is a display issue chance are this could be corrected with a log out and resetting your UI. if this doesn’t happen opening a ticket is the next best option. As you’ve stated above, if it’s taken longer than normal… this is due to others having issues since the new patch.