It's called an existential proof. If you want to prove that a black swan exists, all you need is 1 example of a black swan. Strictly speaking, yes, non-control

It's called an existential proof. If you want to prove that a black swan exists, all you need is 1 example of a black swan. Strictly speaking, yes, non-controlled experiments exist. However without a control you cannot eliminate alternate explanations. Since we know that an alternate explanation exists here, the experiment doesn't show anything. In the case of the black swan there's no credible explanation for that thing you see being anything but a black swan. The control is essentially Occam's razor.