I have 2 tents in bedroom. Mylar base and that 2nd layer tray. Quite a few plants and come and gone. But my question is with all the thousands of gallons of water, what does my carpet look like under tent?
At this point I am scared to even look at the evil from below.
Depending on the tent size you could slide it up to check where its been sitting.
I have spilt so much water(a few gallons b4) in my 2x2 and have left sitting water on the bottom(by mistake). Proud to say no water damage or leaks from the tent. Plus imo most of the water should dry out pretty quick depending on your temps 
I stopped tent growing and moved it to a closet. I kept the bottom liner of the tent and have seen no stains or dried puddles under it when I clean. Been almost 2 years. I kept it specifically for that reason and it has worked like a charm.
