It had drained about half way before my wife got home. It happened while we were all gone, so no idea, obviously nothing hit it unless the cats somehow got really desperate for some live food.
Thankfully for the fish it didn't fully drain so they lived through it. Also thankfully neither of the heaters cracked.
Petsmart exchanged the tank for us, so we have a new one up and running already. We put the fish into our other tanks (20g and a 10g, also a 10g QT tank). We used storage totes to hold all the sand, but they would work for fish too. The QT tank was located under the 125 though, so when it came time to move the stand we had to drain that tank too, so we put the 10 diamond tetras that were in it into one of the totes with the sand. We did it all in a single (very long) day (and into the night).
So I guess that makes me an emergency tank tear down/set up expert
I've been looking into using window security films, I don't know if they'd help (maybe keep the water in if the glass cracked).
EDIT: Here is a video of it (for its intended purpose).