To hide or unhide a BowerKit, head to your Dashboard, find the BowerKit and click to edit. Click 'Edit' and scroll down to the section that reads 'Hide BowerKit - Don't show in Discover'. Check the box.
To Unhide your BowerKit, uncheck this box. Or, on the 'View' tab of your BowerKit, hit the button that says 'Unhide':
Once hidden, anyone who has been sent the BowerKit will still be able to access it. If you don't want anyone to access your BowerKit, you will need to deactivate it.