Sarah and her daughter went to the daughters favorite restaurant for lunch.
This was only a few hours after Les Brown had come to Sarah and David's house around 10:00 AM looking for David because he was no where to be found and the load of pigs had not been delivered. Later that afternoon David's truck was found and Sarah was called on David's phone, to which Sarah and her daughter, along with David's mechanic, responded to where the truck was found parked in the middle of the road. This is apparently when the daughter became sick.
Sarah also mentioned that LE would not let her near the truck because they were using the dog to track David and Sarah's scent may have confused the dog. I don't imagine Sarah's daughter was allowed near the truck as well. Sarah took a picture of the rear of David's trailer, from her car, while parked on the road. I would estimate Sarah was parked several hundred feet behind the truck and trailer, so I don't think Sarah was parked close enough for the odor of the pigs to have made someone get sick. Living in Iowa, one becomes accustom to the smells associated with farms and passing livestock trailers.
Maybe the food she had for lunch upset her stomach. I would think a situation such as this may cause some people to have an upset stomach. However I also think most people would not have much of an appetite if they had just learned their loved one was no where to be found. I know I wouldn't be able to go out for lunch if someone had just informed me my wife was missing.
JMO
I believe this was in one of the many interviews Sarah gave. I will try and find the interview and post it or maybe someone else has it and can do the same.
Link to video showing car behind truck:
Sheriff: No theories ruled out after Siouxland trucker vanished more than two weeks