If a tree falls in the forest and nobody is around to hear it, does it still make a sound? YES.
Just because the pool did not collapse the floor, it does not make it safe.
There was no previous mention whether this was a slab foundation or a basement foundation, so "Engineer" was simply pointing this out in case someone else with a "basement foundation" decides to try this in their own house (it is bound to happen, there are plenty of uninformed people)
I agree with "Engineer" above. If this house has a basement, the floor could have collapsed AT ANY TIME, whether there were people around or not. It is extremely lucky that nothing happened and that nobody was in the basement watching TV if the supporting floor did fail. Believe it or not, even though nobody may live in the basement, it is often considered living space just the same.
If this house has a slab foundation, "piles" that support the house are usually installed around the perimeter of the foundation and underneath supporting walls. The living-room is a large open area with no supporting walls in the center. This means that 12 TONS OF WATER WOULD CRACK THAT SLAB FOUNDATION and exert unnecessary stress to the walls and floor nearby. At best a slab foundation has between 4-6 inches of concrete (except along perimeter walls) and this CANNOT support 12 tons of anything.
Besides the very unsafe nature of this pool installation, I found this story extremely hilarious. The writer has a good sense of humour and her delivery of the story is great. Well done. Please consider your father's advice in the future. :)