The immortal evil

I read that the central head of the Lernaea Hydra was immortal, and unlike the rest couldnít be annihilated by Herakles who instead kept it subjugated under a large rock.
I donít doubt that Herakles would have chosen a very heavy rock, one which couldn't be moved by just anybody; and discovering the buried head of the monster by chance would have been virtually impossible.
Yet now, countless aeons later, with most people having not heard of what happened back then, is it that unlikely modern means for moving weights already equal in strength the demigod and can provide any mortal with the ability to lift even what was once an immovable rock? If so, it is just a matter of time, and inevitable, for the immortal evil to be free again.

I you wish, you can also listen to the narration ^_^