I wasn't particularly clever as a 13 year old. I saw the flag in a YouTube thumbnail for a video about the US military, and the trans flag was transparent, so I thought the blue was darker and the pink was red.

So basically:

Big-ass expensive military = "this is probably the flag of some ebil authoritarian third-world country that prioritizes its army over the welfare of its citizens"

Flag with blue stripes on the top and bottom, and red and white stripes in the middle = the only flag fitting that description I knew of was North Korea

The supposed "North Korean flag" didn't necessarily look right to me, because I swore there was a red star somewhere on the DPRK flag too... buuut when pulling from old knowledge to make sense of new information, the DPRK flag was the only thing that made sense in context. I figured it was more likely that I had just misremembered the DPRK flag slightly than that it was some brand new flag I hadn't seen before.

It was only when I stopped scrolling and actually read the video title that I saw it was actually about restrictions on trans personnel in the US armed forces. I first became aware of trans people even just existing at most a year prior... From my understanding of trans peple at the time, I wasn't expecting "them" (unbeknownst to me, actually us) to have a flag.