Someone found out who I was over email

I responded to an ad of someone wanting a lawn mower on craigslist. They live in a town 45 minutes away and I'm confident they didn't recognize the mower or anything like that. I sent a picture of it and price but never heard back from them. Then a few days later they emailed back asking if my name was "Steve" followed by laughing, which that is my real name. I always use a throw away email with false name when using craigslist so no one robs me. My question is, how would they have gotten my name? Will an IP search reveal this? Kind of freaked me out.