I found it almost instantly, which was by dumb luck.

But in the following few moments, seeing two nearly identical photos side by side soon made me think of stereograms, since I'm into them, and have shot a few in my lifetime.

I then used my eyes to overlap the images.

In binocular overlapped view, the difference loudly draws attention to itself, because it flickers between the two eyes.

It's almost as if there were a blinking LED saying "here it is!"