Once You Have Deleted A Contact In Your Contact List(AOL), Is There A Way To Retrieve It?

Yes you can, first you should concern to a soft wear specialist, and don't  make more entries, because when we make the entries or some other work then the memory address of those entries also saves in the cashes.
It remains save after deleting, but not  many more,  there is a limit of saving the address of the data, that's why concern with some specialist soon.

Yes things can be retrieved but you have to bring it to software engineer as soon as possible. If the time passes on the chances get lowered for retrieval.