the main reason I believe this is because when the monsters smelled them hiding under the truck they were somehow able to disappear despite having no route they could have used to escape... but were also dumb enough to leave evidence behind that they had been there...
Same same. In fact it bothered me enough to check to see what happened in the manga. It's basically exactly the same except when the monster says he smells something, the truck and demons are now outside, having clearly already moved from the indoor location they were in before. Which actually doesn't really change things. But at the very least it seems by the time he smelled them they were at least gone for a while.
Edit: Further reading though it's actually the demon that finds the bunny and he claims it was under the car. So iono it doesn't seem to flow that well. ---
