This is one of the most heartbreaking threads I've ever read. Having just this past month gone through this stress-filled experience of waiting for a mail order shipment of chicks myself, it especially affects me.
One of the values of BYC and heartbreaking stories such as this one, is the instructional value for all of us. There are several things to be learned from this OP's experience.
The first thing to remember, given the precarious state of day-old chicks, is to choose a hatchery that is as close to your state as possible.
The second is to choose a hatchery that ships on Mondays only, and do not order for shipment on a week there is going to be a federal holiday.
Unless the OP fished that heat pack out and placed it with the chicks, I would ask until I find out why it wasn't placed underneath the straw bedding. Those things get very hot and can kill chicks with direct contact. If they were shipped with the heat pack on top the bedding like that, those chicks could have been dead days ago.
And last, even if the hatchery is relatively close, you need to investigate beforehand the number of sorting centers the chicks will be subjected to and what, if any, 24 hour layovers they will have to endure. Knowing this information, you may be able to take delivery a day sooner if you have a friend in the town of the sorting center that they can be shipped to. I elected to do this, and a three hour drive to go get my chicks was worth the effort to get them a day sooner.
I'm so very sorry about this as I had visions similar to that photo just two weeks ago as I was tracking my chicks and they were "lost" for 24 hours and not delivered the day the tracking indicated they would.