Try a couple of places
1.) From either side find the line where the upper fairing and the side fairing meet. Follow that line towards the front, then follow it to the inside. Follow it till it stops almost to the radiator. There is a hole where the upper and side fairings connect together. If that's not it....
2.) Setting on the bike and looking at the cockpit find where the windshield meets the upper fairing at the point closest to you. Look at the upper fairng from the cockpit side and there should be a hole.
If neither one of those spots are missing the rivets, let us know what parts were removed when you replaced the turnsignals.