I have had a look at this rail, and I am not suprised at the top screws coming away, I have never seen such a bad design. How do they expect the rail to carry the weight of a wet curtain without further support.
Depending how useful you are and if you want to spend another �12.99 on another rail. I personally would look into the feasibility of making a support to the ceiling out of the other rail.
Or you could purchase a length of thin flat profile aluminium bar, (available from most Do-it-Yourself stores) then drill a hole in one end and bend the bar over at 90 degrees, this will be for attaching it to the ceiling.
Then cut the bar to length the distance from the ceiling to the bottom of the existing rail, and then drill and attach with a self tapping screw to the rail.
Even nylon cords from each corner of the rail to the ceiling may be another option. Hope you manage it.
Or take it back and have a bath instead.