Here's one I've never come across before:
Found the solution.
The group that sent it to me had constructed a timeline for a GIF (which they didn't tell me). The playhead wasn't in the correct time for the layer to appear.
Deleted the timeline. Everything shows.
Thanks for the views though!
I'm glad you came back on this. I've spent the last 15 mins trying to reproduce it . I never thought of the timeline
I know! Right?
Thanks for trying though.