Fortunately these hydraulic clutches are nice simple systems. So whatever is, and being in the hands of a great shop, you'll be sorted quickly. Can share one bit of potential curiosity based on your description though.
While it may end up being a cylinder problem your mention that it began after it got "hot again" would make me look close around the hydraulic line where it enters the tranny side cover. If for some reason that long nipple got bent a little or somehow any other part of the line was closer than normal to the exhaust pipe perhaps after it got good and hot the fluid reached boiling point inside the hydraulic line. That would account for come-and-go loss of the clutch and it showing up only after the system got got.
Just an idea. Hope you get it all sorted quickly. Good luck.
Mine has overheated twice causing lack of pressure, the first time (two years ago) I found the hydraulic like touching the exhaust just like Twolane describes, I moved it away from the exhaust and let it cool and all was well.
Last week we were riding rt. 14 between Cody and Sheridan WY, very twisty and uphill, and it happened again, however this time the line was not touching the exhaust. I could pump the lever five or six times and get enough clutch to shift. Once we got back to flat roads and the engine wasn't working as hard the clutch was fine, my guess it that the engine/exhaust got so hot that the fluid boiled where the line comes out of the tranny...wondering if there is a way to shield the line from the heat.....