Recover missing images in iPhoto
I came back from Hawaii and I downloaded my photos to iPhoto and now all the photos before and including that
download don't show up in my iPhoto library, just white frames with question marks.
I've since downloaded photos and they show up. I'm hoping that all those photos are recoverable, to say the least. How should we proceed with this?
Answer
If iPhoto is open, quit out of it. Reopen iPhoto while holding down the COMMAND and OPTION keys. iPhoto will then prompt you with options to rebuild your iPhoto database:

In your case, you might be able to get away with simply selecting the option to rebuild the thumbnails. However, if you've got time, it might be best to check all of the boxes and let it do a thorough rebuild.
NOTE: You might see slightly different options depending on which version of iPhoto you have.