How come my computer can't find a picture from my Nikon D300 camera?

I plugged it in and all my pics came up, as usual. But the picture's code is 2724 and it only goes up to 2723… Anyone have any ideas?

Are you looking at the files with Windows Explorer, View NX, or something else?
If it's something else, one possibility could be that you switched to RAW, and the program can't read the RAW file. If this is so, then file 2723. JPG in your camera's display would be followed by 2724. NEF
If it's 2724. JPG, then that is not the explanation.