this is an old thread but i had googled my problem tonight when my wife's phone was giving her "sim card not found" error and boy was she freaking out
She explained that she had taken out her SD card, and somehow in doing so snagged the sim card with it, because they are right on top of each other, and both fell out, and when she put the sim back in, it gave her that error.
Perplexed, i watched a youtube video, read some forums, then i got to looking at her phone at the slot and noticed there's 4 little springs, and the 3rd one over wasnt quite propped up like the others, so she took a teeny tiny needle thing, and moved it up, we slid her sim back in, restarted the phone and lo and behold we were back in business! yay go me
So sometimes the simplest things....