exacc

Anybody experience this? I picked up my car from the shop today, and noticed the rear windshield rattled more than usual. Stopped by the side of the road and noticed that the top portion of the rear windshield (Plastic type) is not seated properly. Pushed it form the inside and it was indeed unseated already. The entire top portion is unseated and the side portion is still sealed.

Is this common? What is the proper sealant to use to re-seat this part?