Hello again, Less Wrong! I'm not entirely new — I've been lurking since at least 2010 and I had an account for a while, but since that I've let that one lie fallow for almost two years now I thought I'd start afresh.
I'm a college senior, studying cognitive psychology with a focus on irrationality / heuristics and biases. In a couple of months I'll be starting my year-long senior thesis, which I'm currently looking for a specific topic for. I'm also a novice Python programmer and a dabbler in nootropics.
I'll be trying to avoid spending too unproductive time on LW ("insight porn" really is a great description, and I've learned to be wary of being excessively cerebral), but here I am again.
This seems to me to be a permutation of the sunk cost fallacy. If you retrace your steps, you feel as though you're wasting the effort you took to get there in the first place, even though it's already spent and now it makes sense to go back again.
I share the intuition, by the way.
Are you sleep deprived? This kind of attention lapse sounds like the calling card of a microsleep.