Hey!
This has been reported to the Development Team who are currently investigating what has happened so they can have a fix implemented asap.
From what has been found it appears to be a visual issue as we have confirmed from players logs that the item is being received on there accounts, but not appearing in their inventory. So when the fix has been implemented Shock Hammer will appear in your weapons tab.
I will post a further update here to let you know once the fix is live.
OminousGMan - Support Human 