You gotta think like a thief.....what has value if I take it? Then use what has no value to conceal your goods.
Although I don't believe leaving firearms in an unattended place is wise, I guess if you are determined to do it, you might as well do it well.
Do you have a well? How about an outhouse? Either one could conceal a pvc tube hung with a cable. I would almost guarantee you the nobody is gonig to look down your shit house with a flashlight. Likely wouldn't uncover your well to search there either.
Got a big round of firewood you use for a chopping block? A hollowed out spot in the bottom would hold a pistol sized piece of pvc pipe...and still function. Who steals chopping blocks? Get the idea?
There are lots of places to hide stuff if you look for places that have no value to a thief.