No, respectfully, I don't think so. If anything the timing makes the hot car death theory more credible, at least in my opinion.
Consider that the parents mentioned it being close to Deorr's nap time in one of their initial interviews. Most toddlers I know nap sometime between 1pm and 3pm. 1:00pm would be the time of day when the temperature was close to its peak. Even though it wasn't a scorching day, research was shared on earlier threads stating that a young child could die in only 20 minutes if locked in a vehicle in sun on a 60 degree day. JM may not have even thought about the truck getting too hot as it wouldn't have seemed overly warm outside. The truck would seem to be the logical, most comfortable, and safest place to leave Deorr to sleep.
I think it is very possible that after the trip to the store, where Deorr jr ate his fries (his lunch), he was put down for a nap in the truck. While he is napping, this would be the ideal time for the parents to get away for some alone time and do some exploring of the creek (maybe they were doing something illegal during this time so lied about it, IDK). Either way, I think they would be more likely to leave baby Deorr alone with ggpa if they thought he was sleeping safely in the truck, than if he running around the campfire. Otherwise it makes no sense, because JM was supposedly on the camp trip to take care of ggpa. Why would she leave her toddler with him if he himself needed a caregiver?
Consider also that Deorr jr's blankie was found in the truck, the truck seemed to be a sensitive issue for Deorr Sr in his interviews, and JM's mom was cleaning out the truck when LE/Search and Rescue arrived. Although there might be some saliva or vomit with a hyperthermia death, his diaper would have caught most of the bodily fluids expelled. There would be no blood evidence, and it would be normal to find Deorr's DNA all over the carseat/truck as he had slept and ate in there and maybe even drooled or been carsick in there before. Any evidence could be easily explained.
If the parents got back from their walk to the creek around 1:30ish, Deorr could have already perished in the little amount of time they were gone. Why they would not just call 911 for help is difficult to explain (perhaps panicked or were involved in something illegal or negligent at the campsite). My theory is maybe they gave him some meds to help him settle down for his nap and were worried they caused his death, making them responsible and subject to prosecution if an autopsy were performed on the body. If they found him by 1:30pm but did not call for help until about 2:30pm it means they had a full hour to dispose of his body and concoct their story about him wandering away. And then maybe another 2-3 hours before LE arrived on scene, to clean up and dispose of evidence.
GGpa would have to be covering for the parents to make this theory work, as he stated that he saw Deorr go towards his parents down to the creek. I'm not sure what to make of his health or mental state, so it is hard to judge if he could be manipulated or coerced into believing something that wasn't true. He may just have felt guilty that Deorr died on 'his watch', even though he wasn't directly involved, so he offered to help with the cover up. Knowing that nothing would bring his great-grandson back, he might have felt it important to protect his grand-daughter, especially if she's had custody issues or trouble with the law before.
Hot car death was my first thought on this case, way back on day two or three. There are so many possibilities and theories, especially when we don't really know for sure if his death was accidental or homicide, so I'm trying not to get stuck on one theory. But I really can't discount it either.
So, it does seem DeOrr was alive after the store? I guess that means I give up the hot-car idea.
