Suggestion:

    Something may be causing something.

Counter Argument:

    There's no proof of that.

Counter Counter Argument:

    Ah, but is there any evidence that 'Something' is *not* causing it.

No, you see, that's not how logic works. You provide evidence for something; not the absence of evidence for it not happening.

There's even a name for it. It's called: argumentum ad ignorantiam (guess what that translates as), also known as an appeal to ignorance.

https://en.wikipedia.org/wiki/Argument_from_ignorance