I don't think he's completely banned. You can still see his profile pic, signature, etc. in all his previous posts, and you can still view his profile. He's either [still] temporarily banned, or just lost interest in this forum.
When you ban someone on a SMF forum, it doesn't delete the account, so other uses can still access the profile. If the profile was deleted, the ban would be gone!
Also - a permanent ban is the same a temporary one, but with the "expiry date" set to infinity