He's a busy guy, I'm sure he turned around, got to doing something and it slipped his mind. OR, he did send them, and they went astray.

You said yourself he shipped a great product, so perhaps you should just privately e-mail him, and politely let him know that they did not arrive, and you just wanted to let him know you're still interested/excited to get them so if they went astray in the mail, or he's been too busy to send them, you'd really appreciate him to send some at his convienience.

Perhaps you can give him an update on the sliders as well so he feels good about doing you the favor of sending you free stickers.

Being able to scmooze is a lost art, I swear.