Same Boat

Same problem with my wife. But I don't think it is my wife fault. She handed over her passport (China) and our son's passport (US) to an officer. That officer checked them and then handed back to my wife without collecting the I94. I guess that officer mistakenly treated my wife as US citizen becasue of my son's US passport.

As far as the letter, just tell them the truth. Check the web, it seems that this happens a lot.

Good luck,