Lots of coins were holed back in the day so they could be worn on a string or sewn into clothing so as to not get lost. Someone back THEN would have drilled or punched a hole in such a coin,nobody TODAY would do that with such a coin. So while it MAY have been on a necklace and lost somewhat recently,the hole was very likely put in it a very long time ago.
Also take into consideration that many very old coins have been found very shallow due to movement of ground during construction,erosion or being brought in with a load of dirt from somewhere else. Regardless of how it got there,it’s a very elusive coin for many hunters,and a very great rarity that one would be dug as a first silver coin. It sure is a nice one!