Strange things happen in cyberspace. I recently had one person email me regarding a horse I had for sale and I replied promptly. I got a message back from the server that the address had permanent fatal errors and could not be delivered. Luckily, she had given her phone # in her email and I called her. For some reason, her email server would not accept any mail from me. Even when I clicked on reply from her email. (By the way, I wound up selling her the horse.)
Another one emailed VERY interested in a particular horse I had. We emailed back and forth several times and I needed to get new pictures. I got the pictures and sent them to her. After a couple of days, I had not heard from her and so I emailed again, asking if she had got the pictures. She replied promptly that she had not. She thought I hadn't had time to get them as a result of the rain and was waiting on me. I resent the pictures and she got them the next time.
I guess the answer is, if it is something you are really interested in, follow up in whatever way necessary. I had one ask for pictures by posting a message on the auction, but never left an email address. I did a Google search, found her farm website, and clicked on the email button from that and sent her the information she wanted.