I know exactly what you mean. I took advantage of the offer of 500 free listings (I didn't quite get there in the time available, but gave it my best shot and got close to 400) but because of the difficulty in searching your own listings I accidentally listed something that was already listed. You'd think by the email response that I received from ebay, I had committed the most atrocious crime.

You are not doing anything wrong when you tick the autorelist - you just don't get an email notification it has happened.