DIY: Wine Bottle Feature For Your Garden 

Johanny Jacobsen I know! It’s addictive!

I'm thinking that they relied on the weight of the wall to keep it wedged in but I'd be inclined to use some extra sort of fastening myself to guard against it coming loose as the wall settles. You could most probably sort something out at the rear of the panel that wouldn't show from the front.

I live in a high wind area as well (although we don't get anything as fierce as tornadoes) and I'd be inclined to rig some sort of fastening to the rear of the wall where it wouldn't show. I thought perhaps setting some anchored wire loops into the concrete while you're making it and running them through some metal rods that are hammered into the ground through the holes in the back of the concrete blocks it's standing on. It would work for my conditions, but I imagine that you'd have to really think about how to plan a garden with the minimum of possible flying objects in a tornado area. I have to consider flying bits and pieces when it comes to my garden - I'd imagine you'd really have to take things to a whole new level in your area.