Thanks for the reply.
I have a couple thoughts.
1) Depending on how the platelets were counted, it could effect the accuracy of the results. This does NOT mean your vet did anything wrong. Cat platelets are notoriously "sticky" and like to clump together on the glass slide. If they were counted with a machine, the platelets can clump together and the count can seem low because the machine thinks a clump of platelets are just one big platelet. The other thing that doesn't quite fit is that low platelets don't cause anorexia and weight loss. Platelets clot the blood. Animals won't have problems until they start bleeding. You will usually start to see small tiny bruises on the skin, blood in the urine, bleeding gums, etc.
You can ask your veterinarian to recheck the platelet count before starting any treatment for low platelets. You could even ask that they send a sample of blood to a pathology lab (unless they did this initially). These labs have clinical pathologists on staff that review the results. In dogs, low platelets occur because the body's immune system will destroy them. This is just not that common in cats. As far as a vaccine reaction, I would call the vaccine company and see if it is a complication that has been seen before. How long ago were the vaccines? If it was more than a month or two ago, this is not likely to cause low platelets.
2) A few possibilites for a cat that does not want to eat and is losing weight is pancreatitis, liver disease, kidney disease, foreign body, inflammatory bowel disease (like irritable bowel syndrome in people) and lymphoma.
I would be happy to discuss Angel's case with you more if you have further questions. I am here to help.