Put a piece of tape, any sort, over the screw after cleaning around it with isopropyl or something similar. That won't stop any oil leaking, but it'll make it obvious if that's where it's coming from. I'm skeptical that enough oil would get past the grub screw to form a pool, but you won't know till you investigate further.
How old is the hub? My oldest one started leaking after about 15 years, but it's very inconsistent, sometimes it was after a long ride, sometimes when I'd just been to the shops, sometimes not for weeks, I tried to be consistent in the way I parked it, but it didn't make any difference. I occasionally think about getting it fixed, but instead just follow the oil change method in the Living With a Rohloff booklet, basically give it a better flush and drain most of the oil back out, it's been fine doing that for the last 6 years.
It's up to you, but I wouldn't bother doing another oil change till it's due (I'd also not be buying kits, it's a very expensive way to buy what you need) Rohloff themselves say if all the oil were to leak out there's still enough coating the parts to be fine till the next change.
