Hi All, total newbie to car maintenance here - just changed my oil for the first time on my 2016 Fit EX, standard transmission. No issues with the oil change, but while I was under there I noticed a hole on the bottom of the transmission (?) that looks like a bolt belongs in there.

It's threaded, and there's dark, sooty discoloration around it with a bit of a sheen. I've had no mechanical issues. Did I drop a bolt somewhere? Is this some kind of exhaust/drainage valve? YouTube videos of oil changes and transmission work don't address it, but I can see it in those videos - doesn't look like there's a bolt, but the discoloration isn't showing up on others'. I'd appreciate any takes on what I'm missing here.. thanks for reading