The chance of finding a "new" element in nature, on this or any other planet, is small, very very very small.
As much as I agree this game doesn't have to be built 100% of reality, and what is "realistic", adding an element not excising in the real world (and by that I don't mean in labs where it's made) doesn't seem like a good idea to me.
When talking about the vastness of space, rare events happen all the time. That means that if discovering a new element on another planet is "small," when you factor in something like the Drake Equation, the amount of planets that could have an undiscovered element is quite a high number. Who is to say the alien world in the game isn't one of them? The more you argue with me the more you prove my case, so your disagreement is quite pointless.
As far as we know, creepers don't exist in reality, yet they exist in the game. It's called "science fiction."
Much contrary you're just pointing out your lack of scientific knowledge, an element like 113 (just as an example) has a half life of 20 seconds (I went to check).
A. It's extremely unlikely to be created in nature at all
B. if it were, no matter how impossible this is to happen, it would be gone 20 seconds later.
This is not an element you want to make things out of
Now, the point of creepers is simply silly, for all you know they are a carbon based life form like humans, they are, compared to another element being found on a planet, very likely to exist.
I did count in the vastness of the universe, and I still estimate it's unlikely in the universe.
Btw, the "The Drake equation is a mathematical equation used to estimate the number of detectable extraterrestrial civilizations in the Milky Way galaxy." that has nothing to do with anything in this discussion, so I have no idea why you decided to refer to it.
I do agree with one point though, this is quite pointless, it all comes down to one thing:
I don't like imaginary ores to be added to the game, I think it's senseless.
We can always argue about the reason for that, but it's unimportant in the end.