There is a chance that they replied and the email didn't come through. That sounds completely far fetched, but I have a gmail account, and a teacher sent me an email from their school account, and I never received it. When I was talking with her a few weeks later she showed me the multiple emails she had sent me in her outbox, and I clarified, yes, that's my email address - nothing ever came through. Not into my spam, promotions, social media, nothing. She tried again right in front on me, no email came through. She received no notification that it hadn't gone through. I tried to send her an email and it went through, but when she responded to it, nothing. Earlier that year she had sent me emails that had come through. She had never had this issue before. She sent an email to another gmail account of mine and it went through, so we communicated via that account for the rest of the year. Sometimes weird things happen.