i dont know if this is the same problem - about a year or so ago i had a problem with all my music disappearing after a hard reboot - took into the Genius bar at an Apple store - turned out not to be anything with the phone but with a corrupted version of itunes on my pc (why it happened on my phone is unclear since the phone was connected to my pc when i did the reboot) - the guy at the genuis bar gave me another copy of itunes and i went and installed it (after uninstalling the version on pc) - havent had a problem since
It was the most bizare thing I've experienced with my iPhone. About a month later, they just appeared back in my camera roll. Here's what I've come to a conclusion with:
1. When I took the photos I barely had service, then did a hard restart before I had consistant 4G service. (AT&T)
2. I plugged my phone in to my computer, hoping to find them, looked through my photo steam, hoping to find them, nothing.
3. I rebooted my phone, the camera app, the photos app, each several times, nothing.
4. One day, about a month later, I gave my phone a hard reboot. Suddenly, they were all there. I tried to figure out what about that hard rebooot could have had an effect, and I really have no clue. It wasn't at the same place as I took the photos, I was at work when I rebooted it, on WiFi.
Hope that helps. Really, I have no idea.