Might have seen you then: I was at the Runrig concert, then came back to the Royal Oak afterwards! Didn't come downstairs until late on, after upstairs got a bit too noisy!
The Royal Oak festival run has just started now, something great on every night as well as the usual sessions.
Any other visitors to Edinburgh Fringe, also check out the "Acoustic Music Centre" at St Bride's Centre, off Dalry Rd: not quite in the centre but on a good few bus routes. (44, 4, 25, and several others)