Did you leave a reference post? While it's not guaranteed a post will be made, it is also not written who should leave the first post.
I make it a point to leave feedback as soon as possible. Before I do, I contact the buyer to make certain they were satisfied with the transaction and then I leave feedback for the buyer. If the buyer was not satisfied, I'd try to correct the situation ASAP; this scenario has NEVER happened.
The gist is you should leave feedback first.
Back to using POGs. Why did I ever leave you dear friend?