I wanted to collect all 15...but it does not look like all are represented in the game.........right?

So for now its just 8 balls in my megaton sink.

....
For what reason did you put this in the Fallout Universe forum?

damn....umm....aliens did it...or my cats...while I was away.

http://fallout.wikia.com/wiki/Pool_Ball

Worst thing about the pool balls, and inexcusable in my opinion, is that they don't fit in the triangle! Ooohhh, my rage is bubbling up even thinking about it.

At least you have time to try that, I want to see if they can

On my very first playthrough I started collecting pool balls (it's bad enough that there isn't even a full set), then when I found a triangle I was overjoyed.... Stopped whatever quest I was working on and ran back to my Megaton house. Drop the triangle and start to pick up the balls... wait a second... only three fit. WTF!!!
I`m sure it was some kinda scaling issue, like the balls woulda been too small or the triangle too large, but... c`mon.

Futile... Maybe use the geck editor. Ultimately futile? Try reassembling that chess board found in that Zone 2 Tower.