Maybe left over from the oil pump cover leak, or the repair is leaking.
IIRC one person, maybe two, replaced the gasket for that plug but IMHO it wasn't clear the leak actually came from there.
There have been, rarely, leaks from the timing chain cover where it mates to the block but then you should see signs of leaking higher up along the sides of the cover. One of those leaks is directly above the oil pump cover in a "corner" of the timing chain cover but IME that one has been a very slow seep.
Wash off the bottom and lower front of the engine (avoid the distributor and top valve cover) and watch closely to see if the leak returns.