how do you find missing titles, effects, and generators in final cut pro x?

Actually, that's only one of two questions...

ONE

When I attempt to export a movie, uncompressed, not through Compressor and not sharing to an Apple device, I get an error saying my Project has "missing or offline titles, effects, or generators."

There is a little yellow warning triangle next to the project name.

But there are no little yellow warning triangles next to anything in my libraries, and everything plays through in the Timeline.

Before exporting, how can I identify the supposedly missing elements???

TWO

After attempting to export the same movie via the Share item to an iiPhone, i received a Quicktime Error: -50.

Interpretation, please?