Presumably if we're dealing with a non-human intelligence that does not want to be identified then we're in the challenging situation of this being closer to an adversarial war than a natural phenomena. So, while absence of evidence doesn't prove anything about that being the case, absence of evidence would be expected if it was: if human civilization developed ubiquitious high-res sensing tech, then you'd expect the adversary to respond in kind.

In other words, if they're real, and they're trying to hide, then the fact we all have iPhones hasn't yielded more evidence doesn't prove anything, because if it was us, we'd change our tactics to avoid being detected by those things. As we do in war. It's very important to notice I'm not saying this tells us that is what is going on - we have to build up our priors in other ways to decide if that's true - but what I'm saying is that the claim that we all have cameras and yet not more UFO videos has absolutely zero epistemological effect, since it's smuggling in the assumption these objects are behaving like a natural phenomenon that will maintain their visible presence in spite of our own technological advancement. That's obviously not what one would expect if it's actually non-human intelligence.