Have you considered gallbladder? Gallbladder attacks are inconsistant in their symptoms. For example I had crushing back pain and vomiting. My aunt had heart attack symptoms and shortness of breath. It took 5 years for the docs to diagnose me and I kept telling them its my gallbladder. Just a thought and something you might want to read up on if it happens again.
You know, my husband keeps saying he thinks it's my gallbladder. The doc kind of wrote that off as a possibility, but we know that doesn't mean anything! If it happens again, we'll know to see about that. Thanks!