You are not sick from BT corn (which is presumabley the GMO you're talking about)
how can you make this statement when you have no idea which corn she/he was eating?
with over 80% of the corn grown in america being GMO, there is a HIGH likelihood that is the corn she/he was eating.
because of the extra time and money, coupled with decreased yield, you are likely to know by the price if you are buying natural corn. (hint: its not cheap, and not nearly as common)
if it doesnt say it is natural/organic, it is likely GMO. as in america that is considered "conventional" farming.