@Gala,
Like GWitch, I've designed hundreds of gardens, and haven't heard that any sculpture was taken from a clients front yard space - on the other hand I've tended to tuck them into a planting area (even if they are a focal point by definition) and they tend to be heavy. And, I am more likely to put a fountain or planter in a front yard garden than a standalone sculpture.
On the other hand again, I had a garden sculpture taken from my front porch. I had a glass windscreen that rested on a concrete wall, the wall having a kind of shelf on either side of the glass apparatus. That's where I put the concrete dog - fairly heavy but not impossible to lift - that a friend had given me. And that's where someone came up the steps to the porch and took it.
I never did decide if it was just too charming to pass up or if it was fodder for the drug purchase mill like gnomes can be. I hope in retrospect that it was taken for the charm and that the guilty party is enjoying it.
