Glued grip has rotated, won't rotate back
It seems a bit unusual to me that your grip would be actually 'glued' to your handlebar. Typically grips hold themselves in place, but I'll take your word for it. =]

If your grip is in fact 'glued' in place, the adhesive is likely mediocre quality, and rotation you're experiencing is due to heat from your hand and/or the outdoors slightly softening the glue. 

You may be able to un-rotate the grip by heating it with a hair-dryer, and therefore softening the adhesive to a point where you can move it by hand. Be careful not to burn or melt the synthetic leather, though!