I just shot a bunch of photos with my Nikon D7000. After each photo it was displayed on the LCD Screen but when I went to download the photos they are not on the camera. I've used this camera for almost 2 years and have never experienced this. Help!
The D7000 has dual card slots.
If you mistakenly didn't have a card in either, then you would have been in "demo mode", which is something you can use to look at shots in the camera store to evaluate the camera. Images are stored in-memory, but you cannot download them, only preview them on the LCD. Usually the LCD will display "DEMO MODE" to indicate this.
If you play back the shots on the camera, are they still there?
If you had cards in both slots, then it's possible you're trying to download images off the wrong card.
If you are connecting the camera directly to a computer, you might try removing the card(s) one at a time and using a card reader.
It is possible that it is due to a corrupt card.
I once lost a whole day of shooting on my old Sony A100 because it would shoot and display on the LCD, but the camera was only storing the last photo. At the end of a day of shooting (on a whistlestop tour of an Icelandic glacier I couldn't get back to during the trip!) it had only stored the last shot.
Reformatting the card made the problem go away. I read later that the corruption may have been caused by doing lots of deletions on camera (not sure how true this is) so since, I have always tried to never delete photos from the camera itself, just reformat before each excursion. The card was also a budget no-name one, so since I've always gone for top end SanDisk.
I've never had the problem again.
Of course as I can't reproduce this, it may just have been a temporary A100 bug and so not applicable, but it is worth considering.
EDIT: As this does not wholly answer the question "where are my photos", the answer, if the above scenario is correct, is "probably gone". I never managed to recover them. It was a long time ago now, so I can't remember if I managed to try a recovery program on them, but that might be worth a shot to see if you can get anything back!
You might have accidentally locked the SD card when you inserted it into the USB hub; it's happened to me many times. Check the side of the SD card; there is little switch there.