Additional to a small refillable notebook, I've kept a 2-hole journal in my pack since 1996 and virtually every exposure is accounted for.
The journal (my "Little Red Book") contains information on location, position/triangulation, route info, exposure, camera body, lens, filter, film and any extra observations about light and the environment, the latter recorded separately.
Last Sunday night I photographed star trails and diligently recorded the descent of Venus, shortly after observing a quite striking flash as a star fell from the glittering chandelier in the heavens to the silent depths far below. Exposure wise, I recorded: 1hr, 15min Bulb exposure on Provia 100 @EI125 with additional –0.3 (to add contrast for the stars given the light from Venus), TS-E 24 with +8mm shift and +4° pan tilt aimed 45° up at the Small & Large Megallanic Clouds, skylight 1B, position markers at 20m intervals (flashing red LEDs so I can locate the camera through trees: I stayed on a friend's 69acre property and it was a long walk from the cottage to the location), 3 snakes ("identity unknown"), 6 curious kangaroos (these big guys pose a hazard to an unattended camera by knocking into it on their night rambles, so I attach an iPOD to a tripod leg belting out Puccini's Nessun Dorma to shoo them away), a dry, 24°c temp at 10.40pm, light ESE wind and a starry, starry night! It was gorgegous, like so many hundreds before it (and to come...).
Much of this information is separate from exposure info (that is, there are 2 notebooks with links to exposures). I don't keep a record of exposures made with digi camera.
So, a notebook in your bag can serve as a repository for memories that may have faded but could well be nurtured back with great nostalgia in years / decades to come.