Ask Mr. Smarty Plants

To start with, don't panic. The yucca, native to Central Texas, is a remarkably sturdy survivor plant. Remember that it is basically a desert plant, where all manner of disasters can happen to it. I don't suppose there is much problem with chain saws in the desert, but there are lots of other hazards and the yucca is still around.

First, before you do anything else, you need to ask yourself if this vandalism is likely to be repeated in the area where you have planted the yucca. Is it near the street or in an area easily accessible to foot traffic? Is it somewhere that it could intrude on a footpath or sidewalk, or block a view backing out of a driveway? Possibly it was just senseless vandalism, but vandals can be senseless more than once, and you might consider moving the yucca to a more protected spot.

Here is a previous Mr. Smarty Plants answer on transplanting and/or trimming a yucca, which we hope you find reassuring. Another previous answer is from someone who deliberately cut her yucca off, and then started wondering if it was going to survive that. In another answer, the writer's husband had mowed the yucca down.

In terms of the drooping, yellowing leaves, this could well be the result of transplant shock, and while the unwanted pruning didn't help, it may not have caused that. Your best plan now, if you decide to leave the yucca where it is, is patience. Don't overwater and don't spray it with water or anything else, water into the soil around the roots. We're betting on the yucca!