What happened to the OP makes no sense to me. I just had something similar happen, was long 10 GMCR 115 calls into expiration today. GMCR closed below 115, so options expire worthless. After the official close at 4pm, some news drove the stock up to 116. I called IB just to make sure there was no chance of exercise, and they confirmed that settlement is based on the 4pm close. ...Well, at least I hope the IB rep was not mistaken & I don't wake up to long 1,000 shares on Monday. IB customer service dis-functionality is on par with the government of Nigeria, unfortunately.
Since GMCR close under 115, you will not have your calls auto exercised. It would have to have closed above 115 for this to happen. Doesn't matter where the stock trades after hours. If you were short the options, it would be a different story. You would then potentially have the risk of your options being assigned.
http://www.cboe.com/LearnCenter/Concepts/Beyond/expiration.aspx http://www.nasdaq.com/article/autom...k-and-other-options-expiration-issues-cm45720