Sorry to hear that you lost your baby BTS. In my opinion I really don't think anyone will be able to accurately diagnose the cause of death without doing a post mortem exam, but I really do not think that a few crickets killed your skink.
I am also definitely not saying that your choice of bedding or food caused the death of this animal, but when I was breeding BT Skinks or any other herp for that matter. I try to choose substrate that cannot be eaten. Good choices would be newspaper, indoor outdoor carpeting, or paper towels. These substrates may not look as nice but I have never heard of an animal accidentally ingesting it.