If the file isn't part of a book, make it one, then:
Add > List of > Figures
and you'll find out what page it's on (if LOF catalogs missing imports, which it may not).
You can also save as MIF and look in the MIF for the object name. You need to learn a little about MIF to decipher where that maps to in the document.
Import references can hide in all sorts of places, including but not limited to:
- beyond edge of anchored frame (had 2 of those just today)
- hidden behind an opaque something you can see
- conditional text currently turned off
- text flowed out of sight on disconnected page
- in plain sight, but hidden by Color Views
Worst case scenario: create a 1x1 pixel white object and give it the name of the rogue.