I think I maybe have found the a more likely cause.
I didn't have him on heartworm medication so the vet gave me one pills of Iverhart Max Green 25.1 to 50 lb to give him while I decide whether I want to buy more months supply. The main active ingredient is Ivermectin as reflected in the name...and Ivermectin is known to be toxic to Collies and Shelties.
Ivermectin-Wikipedia
The wikipedia article states that toxicity typically isn't observed when the Invermectin is less that 100mcg/kg
IverhartMax Product Information Based on this website the pill I gave him contained 136 mcg Ivermectin
His weight was 29.50 lbs that turns into 13.38 kg. So there was 10.16 mcg/kg in his body. That's a tenth of threshold for observed toxicity the author on wikipedia provided, however, I don't know how generally applied that threshold is to all of the breeds listed. It could be a lower threshold for Shelties.
Sheltie Nations Page on Shelties and Heartworm Medication
I didn't know all this information about Heartworm medication and the possible risks. She actually gave me the extra pill to give him as an after thought while I was waiting to pay at the front desk, like getting a mint from a restaurant. Like I said...I just innocently accepted everything the vet gave me as safe.
Chris, I don't really hold malice towards her. I know I've made plenty of mistakes that cost others a lot more than I know. I don't think I could ever be a vet or a doctor because there just just too much responsibility. My vet did call me back...said she had called the companies of all the pills and vaccinations we gave Pockets that day. Of course none of them reported any more adverse reactions, so she is just as much at a lost as I am.