You should know there are spoilers below.

Well, I'm talkin' about the keyblades in Deep Dive. Firstly, you see the dual-wielding Unknown with two keyblades with the Oblivion and Oathkeeper keychains. Then he runs up the building, Riku jumps off and he throws the Oblivion to Riku. Then he takes out a Kingdom Key, perhaps Sora's, but I'm not sure. Then you see Mickey doin' all sorts of flips and stuff until he lands on the roof of the buidling holding his inversed Kingdom Key. So there's at least four keyblades, like I said.

I do believe Riku's keyblade was destroyed. I'm not so sure however if it was created by the hearts of the six princesses, as we never see how he got that keyblade or where it came from. After Ansem took over Riku's body, he just had it, and I don't remember any explaination of where it came from.