Do you have a SD card in the phone?
If you do, there are two locations where you can find the pictures stored. It depends on how the camera settings are set up.
On the phone itself under DCIM/Camera and on the SD Card/DCIM/Camera
I note that it claims there are 649 images stored in that folder, but it is odd that you can't view them.
There was one other thread on this same subject, but I did not bookmark it and don't recall if there was a fix.
I'm a bit surprised that you took all of those pictures w/o reviewing any of them while on the trip. When was it that the problem occurred that they were not viewable? If you can track down something that was changed on the phone, maybe that will help us to help you.