It has been my experience that if that was your only request, the chances are very good that you will not have a room preassigned. It is easier and more flexible for the resort to assign that when you check in. It can also work out to your advantage that way since you will probably get a room that's ready instead of waiting for someone to checkout and having to get the room cleaned before you can use it.
One other thing that may or may not have happened in your case is the reluctance of the resorts to give out information about what room has been assigned to anyone for security reasons.