How to re-attach ceiling cover?

I have a plastic ceiling in my bathroom which is inter locked to cover the whole roof. Last night a section in the shower came away slightly and droped about an inch. The whole ceiling is attached with a bonding adhesive and has been solid for over two years. Without taking the ceiling down how can I attach it back to the ceiling.Using screws would be a last resort as it will spoil the affect of the ceiling.

Gary P
January 2012