A bug is causing players to lose items obtained from the Trading Post. Blizzard responded they’re aware of it and are working on a fix for the issue.

The bug results in frozen items being invisible and other shenanigans that we covered earlier today.

(Source)

We’re aware of the issues people are experiencing and are working on them. Of note, if you froze an item from last month, don’t refreeze anything else. We believe this is a display error that we are working to correct. Players will likely need to log out and back in once the fix has been added to the game to see the item again.