Although not direct like the one today but here is another example of a foreign object causing a goal. A paper ball caused a corner kick, the resulting corner kick was then scored. This was from the UEFA Cup semi final match between the Hamburger SV and the SV Werder Bremen on May, 7th 2009. Maybe it is time for F.I.F.A. to clarify the rule on foreign objects.
Thanks to @BeateSkj for submitting this.
VIDEO : Another foreign object that caused a goal
The rule states that if a foreign object effects the play, the game is stopped and a drop ball should be given