I'm not familiar with details on any hot car death but this one (I'm familiar with the overview of many of them, though).
Some of the differences in this case:
*it was his normal routine to drop Cooper off (often a deviation in routine causes the parent to go into auto-pilot mode and they forget they're supposed to drop the child off)
*he literally had to have forgotten Cooper was with him in less than 3 minutes, based on the location of the Chik-Fil-A to the turn he had to make to the daycare
*he is on camera appearing to choose a somewhat secluded parking spot, where Cooper would be less likely to be spotted by passers-by
*the car seat was positioned rear-facing in the middle of the back seat, and at Cooper's height the top of his head would have been visible just over JRH's right shoulder, and JRH had to lean to the right to pick up his bag (from the passenger seat floor area I believe)
*the car seat was too small for Cooper and likely had been for at least a couple of months, which isn't remarkable by itself, because many parents might make the seat work longer than it should because they can't afford a new one yet, but they had another, bigger seat for Cooper already, and JRH made statements to police about how he knew all about the car seat Cooper was in, so he clearly knew it was not the right size for him
*and...I need to search for a source on this part, but I believe it was part of the testimony that the car seat straps were set on the lowest setting, as they would be for an infant...so even if they were trying to wait to get a 2nd bigger car seat, the straps should have been adjusted properly since JRH knew all about the seat
(As an aside, it is very common for parents to leave car seats at the day care so the person picking up has a seat for the little one, so even if JRH and LH could only afford one bigger seat, there was really no excuse for them to continue using the infant seat)
*he returned to the car during the middle of the day to put away the light bulbs he purchased during lunch
*he sent his friends a text saying he'd be late to the movie, yet he left work early in order to get to the movie
*detectives testified that there was a noticeable odor in the car even hours later when they examined it, yet JRH entered the car, never put the windows down, and drove at least a couple miles while in the car with the odor, and said he only noticed Cooper was still in the car when he glanced over his shoulder to look for cars so he could change lanes
*and of course, his activity on that day having conversations with six women, and his computer history revealing he had watched a video about animals dying in hot cars and he had been reading a forum about child free living, and his text that morning to a woman said something along the lines of he loved his son but missed his freedom
I think there was one other case I've read about where the woman got in the car and drove with the child in the car. She worked at a university I think, and the child was about a year old, give or take a couple months.
Another difference is that Cooper was a lot older than most kids who die from being forgotten in the car. It was highly unlikely that he was even being quiet - he was 2 and had just had breakfast, it wasn't like it was nap time.
So...those are off the top of my head. From what I know, it's a lot different than most hot car deaths.