No oil in Transmission

[RPB111]

I just bought this '01 EC250 and I have put in three rides of about 30 miles each ride. I decide to change the transmission oil but not one drop comes out. When I bought it I noticed the clutch would not disengage when I pulled it in unless the engine was running. I thought that might be a Gas Gas Hydraulic clutch thing. It has been doing just fine on the trail and is doing better since I put oil in the transmission. The clutch now disengages when I pull it in without the engine running. I do not see any leaks. What should I look for and what kind of damage can I expect to see in the future from this episode? I will run it a few minutes and change the oil again to see if any debris is in it as soon as I get the chance. The oil sight glass is too dark to see if there is oil in the transmission.