You take Sagan's point out of context, first of all. Secondly, while it is true, Sagan also allowed that something can indeed, be proven false.
From wikipedia (the same one you selectively quoted from)
Argument from ignorance, also known as argumentum ad ignorantiam or appeal to ignorance, is an informal logical fallacy; it asserts that a proposition is necessarily true because it has not been proven false (or vice versa). This represents a type of false dichotomy in that it excludes a third option: there is insufficient data and the proposition has not yet been proven to be either true or false. [ 1 ] In debates, appeals to ignorance are sometimes used to shift the burden of proof.
General forms of the argument:
- P has never been disproven therefore P is/(must be) true.
- P has never been proven therefore P is/(must be) false.
Carl Sagan famously criticized the practice by referring to it as "impatience with ambiguity", pointing out that "absence of evidence is not evidence of absence". This should not, however, be taken to mean that one can never possess evidence that something does not exist (one can possess such evidence). Instead, Sagan's famous quote is a reminder that inferences must be made carefully, and that science makes no claims to absolute certainty, only high probability.
So, for the sake of this discussion, it seems appropo to say that there is a high probability that god doesn't exist.
There is a small probability that Jesus is looking at this conversation and laughing his ass off.