Photos disappeared from photo list; still can be found through Faces.

Running Mac OS X 10.7.5. Purchased a separate detached photo digitizer, scanned photos to Scandisk, inserted Scandisk to iMac, and successfully imported all 60 photos. Used iPhoto to rotate, edit, crop, label, and face identify all the photos; no problems occurred. Went back to scan one more photo, and when that photo was imported, all the prior 70 photos disappeared from the Photos list under Library and from the Last 12 Months Import. I can still find the photos singularly under Faces, by the faces I identified, but I cannot find the photos in any list. The photos are not in Trash. Cannot find the photos in Finder or in any list. The photos seem to be on the computer someplace, because if I remember a name, and go to Faces, I can find one photo at a time. How can I find the photos and reconnect?