Advanced Systems Concepts Software Engineering interview questions

I applied online and it took couple weeks for them to contact me. I spoke with the HR person who called me late and didn't spend more than 2 minutes talking to me. She forwarded the call to the director of engineering who had a good conversation with me about their systems and the work an intern would do. I thought the interview went well as I told him the things I've done and my resume. After waiting a week, I emailed them thanking them for the opportunity and to show my interest, the next day the HR lady emailed me back rejecting me. I was baffled because I had a good interview, but then again I might have seemed like I was hassling them with the email even though all I said was I was looking forward to hear from them. It was a disappointing experience, but a learning one.