Yes, it is a bit late, but why not give it a try. Call them back, and ask if the offer is still available. If it is no longer available, don't worry, at least you tried. You won't ask yourself what if, someday. Just make it as a lesson that from time to time you need to check your call logs. But in case the post is available, your lucky enough, maybe you are the one they are waiting for. So, just call them and check the status.