Shatter is a physics based effect that makes this shatter by a force. If you want to reverse the direction of your shatter then you have to precompose your shatter effect and then time reverse the layer or use time remapping. I usually use custom shatter maps and custom layers for foreground and background. If you do the same you have to pre-compose all of the layers used as a reference in Shatter.
I hope this helps. If you're completely lost when it comes to pre-composing and time remapping let us know. There are a bunch of tutorials on that on the web.
I was hoping there would be around the physics part. If you have any other ideas of how I could accomplish this, let me know. I'm messing around with it now and seeing what works and what looks good. I have a few screen shots of what i'm talking about.
Where the logo starts and shatters:
The ugly transition between start and end:
And where the logo ends up as a bug, with all the pieces recollected:
You're making it too hard. It's nearly impossible to match start and end points for a smooth transition without time remapping.
Start your explosion about as you normally do at about 3 seconds into the comp. Let the particles completely exit the frame.
Now pre-compose the layer and then apply time remapping to the layer. You'll see two keyframes. They represent the normal in and out point in real time for the layer.
Go to the point when your pieces are at the farthest point you want them to go and set a new keyframe. Now go back in the timline and pick the point just before the pieces shatter and set another keyframe. Copy this keyframe and move to the point in the timeline (about 12 sconds) and paste the keyframe. Now delete the last keyframe.
The logo will shatter, the pieces move out, then stop and reverse direction and re-assemble themselves into the logo.
I'm not sure if the logo changes into a different shape. If it does then you'll have to do this twice. If you use exactly the same shatter settings for both copies and make your transition when the particles stop it will magically change before your eyes and be seamless. Time remapping makes it easy.