Another is that your own email server (Yahoo, Earthlink, Comcast, etc) thinks the email is spam and never forwards it to you. Check your defaults and settings with your ISP.
Another is that someone is "spoofing" a Hammock Forum address while sending spam, so HF gets put on a "black list" that your ISP uses, so all HF is blocked by your ISP. Usually this is temporary.
Another is that it gets to your computer, but your own email software thinks it's spam, and sends it straight to your junk mail or trash folder, and never tells you. Thus, it's on your hard drive, but in the "wrong" folder. I see that happen a lot with various kinds of email, when I help people who claim they never got this or that email (from a listserv I help moderate).
Most of the above are good reasons for HF to send out a series of expiration warnings, not just a single one immediately before the cut-off date.