If you search for specific terms and they're not in the title/description, you'll actually filter out the comic you want, so it's better to search for things you know are there. For example, if you're sure it was listed in a certain genre, search that genre.http://www.smackjeeves.com/search.php?s ... mat_all=on
That searches for only Donator and Premium comics. There are 33 pages of results, 12 results per page. It's feasible to just look through all the banners and maybe one will stick out as familiar. If it hasn't been too long since you first found it, maybe its subscription is still going. If not, then I really don't know what else I could suggest... it's a long shot, but if you remember the rough page count on that comic, you could sort by Most Pages and navigate to that range and look at banners there.