Revealing mistake: When Jo and Bill are running past the sunflowers, just after the barn has flown past them, the sunflowers aren't even swaying. Sunflowers would blow over at a tiny breeze, let alone an F5 tornado blowing around them. (01:36:45)
Revealing mistake: While driving the red truck through the rolling house, Dorothy is mounted on the back of the truck. There are some very sensitive and fragile instruments located on the top sides of Dorothy that stick up above the cab of the truck. These would certainly have been torn off while crashing through the walls of the house, turning Dorothy into a useless pile of junk.
Revealing mistake: They wouldn't be able to walk or run nearly so easily when near a tornado. In ametuer video footage of real tornados, the people could only move quite slowly, and were walking on an angle of 30 degrees from upright.
Revealing mistake: When they are at the drive-in movie place, Melissa comes out of her room when she sees the wind blowing through the curtains. When she steps out, other windows in the motel are open and the curtains are absolutely still while the curtains in her room continue to blow.
Revealing mistake: When Bill and Jo are driving towards the first tornado together (arguing), it's clear there's no windshield in the red truck. There's no rear view mirror and it's perfectly clear. During the next few scenes, a rear view mirror appears and there is mud on the windshield around the wiper tracks.
Revealing mistake: The weather really is unusual in Oklahoma, as in some scenes, the cornfields were ripe and brown, and in others, they were fresh and green. Obviously shot at different parts of the season.
Revealing mistake: During the scene when the repair shop is falling apart from the tornado, a wire can be seen pulling the drive in theater sign into the building in a brief shot.
Revealing mistake: In the opening scene, where Jo is very young and her dad and mom are carrying her and running from the house to enter the storm shelter, the tornado is just 60 seconds or so from destroying their house and sucking Jo's dad away. If you look at the trees behind them as they are running, you can see the trees are barely moving from any wind at all. If a real tornado was that close, the trees would be half bent over from the 60-100+ mph wind.
Chosen answer: I imagine they just left it at the house where they loaded the Dorothys. You only need a couple of wrenches to remove a camper top.
Grumpy Scot
They were not at a house.