I was away from home for about a month. A friend was watering my trees. When I returned, my acacia tree seemed to have been almost uprooted out the sand. Most worryingly, a portion of its trunk had snapped clean off. I pulled the bottom part of that trunk out of the soil (it was just sitting loose). This was a tree that I repotted only a month or so ago.
I need help as to what I should do now, please. I am still new to bonsai and have not experienced anything like this before. I do not know how this happened to the tree (maybe in a storm while I was out of town). Should I repot again submerge the roots properly?
I am including a photo of the tree after it was repotted, a photo of it after the damage, and a photo after the damage showing the piece of the trunk that I pulled out.