Ok, sounds like you recorded that the right way then. I don’t own a UR22 but I think it would be strange if the UR22 couldn’t monitor in stereo 
edit: seems that’s exactly the problem. From the sound on sound review:
In that case you have 2 options: either use direct monitoring when recording and live with the fact that it’s mono, or lower your buffersize and monitor through Cubase and live with the delay (which is unnoticeable if your DAW can run at the lowest buffersize.)