With the Shop Hop coupon codes, like was mentioned, the shops don't have it in their system. They usually have the special comments section, so I put "I won shop hop certificate #___ for $10". I also forward the shop hop certificate with that information to their email address (usually the one that they send me an order confirmation with) to make sure it's picked up. The first certificate I won - no problem.
I won one in the last hop and it wouldn't apply to shipping, so I canceled the order. She charged my credit card and it took a few weeks for the charge to go off my card. Not the best experience, but she was prompt in calling me back to explain what happened.
For the comment about how the shops should email you when you won - I do like the idea of a congratulatory email, but I wonder if they're given all of our information? From the ShopHop perspective, I would only release a first and last name. The last thing I would want (if I'm ShopHop) is for shops to add my hoppers to mailing lists. I would get a lot of angry mail. So perhaps they don't have your email address so they can't email you...?