Here is what is happening as stated by Blackhornet:
<img src="https://dl.dropboxusercontent.com/u/5426011/fixed/Creation_picking.GIF" border="0" />
And here is one possible way to get your function to work:
<img src="https://dl.dropboxusercontent.com/u/5426011/pics/picking_new.png" border="0" />
The first mirrors your issue. The for-each will only affect existing sprites. The second waits until the end of the tick to do the actions when the new objects are pickable.