@martj-2 : Before dropping the index I tried "DBCC FREEPROCCACHE",but it didn't help 🙁

Will "DBCC FREEPROCCACHE" clear the old plan ?

@Erland : i do understand,without Query or Query plan its hard to bring the solution.

I'm trying to find out all the possible outcomes if i drop and create the index?

If i get that, I can avoid the "dropping & recreating index" and go to direct steps(example:freeproccache,updatestats,etc..).