Or maybe they were trying to use an IR camera or something techie like that..?
While this episode does play Temporal Cold War with the timelines, it DOES mostly confirm that things are at least a little as Doctor Who describes it:
People assume that time is a strict progression of cause to effect, but actually, from a nonlinear, non-subjective viewpoint, it's more like a big ball of wibbly-wobbly, timey-wimey... stuff.
In other words, what with all the time travelling and butterfly effecting stuff happening throughout the franchise, some stuff DOES happen, some stuff is erased, and some stuff just ends up happening anyway. Multiple time incursions move the goalposts on major things - the Eugenics Wars have been established in at least three different centuries by now, NOT including this episode - but they still happen, even if the "prime" timeline changes the minor details.
In other OTHER words, canon is tricky even without time travel, but time traveling through the franchise gives us a convenient "out" on a lot of the niggling details. As with an average Simpsons episode after thirty years, stuff will contradict other episodes constantly - but as long as things are consistent WITHIN THE EPISODE, everything else can be forgiven, no matter how much it riles us continuity nerds up.
In other other OTHER words, the writers are giving themselves license to continue to tell great Star Trek stories like this one, without being a slave to continuity and technology like we nerds would prefer. Thing is though, they ARE using technology to support the explanation, and even if it gives use a preztel-headache, it still works.
Mark