Panoramic Roof repair

[740iS]

Hey all, have a 2006 X5 with a panoramic roof. The roof tilts open and closed without issue (surprisingly) but the rear inside cover appears to be missing. I can only assume it is stuck inside the headliner in the rear. But when I try to open the sunroof, the forward cover moves back to just forward of the headliner opening and stops. Then the sunroof doesn't open at all. Push the switch forward and it slides back where it belongs but the rear cover never appears.

Any ideas on how to get this all back together and working properly again without replacing the entire sunroof cassette? I've read a huge number of posts, but can't seem to find one that addresses this issue.

Thanks for the help!