I fortunately haven't had a stand stolen yet, and here's what I do as a precaution. The stand that I use with a climbing stick, I just take the stick down when I leave and carry it a few hundred feet off and hide it under a fallen tree or leaves.
Screw-in steps are not legal where I hunt, but when they were I used to back out the bottom 4 or 5 steps and also hide them. If they can't reach your stand they can't steal it! (Or at least it's harder for them to do so)
I also as an extra precaution use a bicycle cable and lock as an added measure.
I have a pretty expensive Summit climber and even though it's not too bad to pack in, it's hard to do so quietly and conveniently, so I also hide it under the leaves and take the seat pad with me so it doesn't get wet.

The extra advantage of hiding it under the leave is that any fabric on your stand will absorb the smell of the leave and offer a natural cover scent.
I also engrave my name and address on my stands in several places.

I read another post in one of these forums that I thought was a good idea, and that is to also engrave the words. "I do not sell my treestands, so if you are buying this stand from someone, it is stolen! Please notify the police"
Good luck and I hope you don't have any more stands stolen! It's a shame that there are such slobs in the woods posing as "hunters"!