"you are so lucky"!!
typo alert methinks!!
The only other small plug that I can think of like that lives in the front of the block, capping off the end of the main oil gallery, the rear one has a pressed in steel ball bearing, sometimes these leak, I always knock these out and tap the block and put a proper "bung" in there.
Thinking about it there are 2 very small caps at the front covered by the auxilary/jack shaft seal housing, but of course these can't find there way into the sump.
tabetha