the promo's are sorted by artists that sell the most, and the old ones never leave the list unless they remove it themselves. so even after indexed, it may not show up. it also has no name so it's hard to find your name. the only way those really work is if you announce it to everyone off the site that you have it. but you only have a week to do it in.
i think promo's run differently then a normal picture and i don't think adding tags will help. promo's are something for your newsletter or blog, and to be honest i've ran them before and never had even a nibble. there are quite a few things that need to be ironed out in that area. old stuff should leave the list, but it doesn't. i often forget about the ones i have and i bet they are still there, totally expired.
i can take a quick look to see if your there, which ones are they?
i will say it's due to the problems with indexing they seem to be always having lately. though i would add the title and your name to the keywords to make it easier to narrow it down later on. you can always renew these promos or make more.