I had a hard drive crash, and I'm in the process of rebuilding the drive. I thought all the files were on another drive as well, and I used it to restore to the replacement drive. However, Lightroom showed some question marks on some files, so they weren't all on the other drive. I also have them backed up online. Maybe Lightroom can help me find others that may be missing (although I hope there are none). Is there a way to set up a filter to show only those files with question marks? Then I can selectively restore just those files from the online backup.