I don't feel this answered the question and I have the same one. I opened the text message detail screens on a particular text and the uid is 0. Most of the time it is a longer string of numbers. I am curious why it would be zero on some texts and not others. If it helps, I am texting an iPhone user and I have an android. They have AT&T, but it also happened when texting another friend that has an iPhone, but I think she has verizon. So my question is why would a text from my android to an iPhone user show the uid in the detail screen of the text at zero when all the text right before it had a longer digit number.