titleist,
I have had awsome luck with 800 speed film from my Stealth Cams! I use Kodak Max, and the night shots are great!
As far as the missing pictures go, the crew at Wal-Mart could either think the pics are bad quality or, you could have another hunter there (or a hunters wife/girlfriend) that takes the pics home with themselves! I would try the note thing or just telling them you want all pics, and if that doesn't work, I would switch the developer!
Here are a few pics I got off my stealth cams at night using Kodak Max 800 speed film....