The very "fact" that you could walk into Tibet, and escape detection, says a lot about the sparseness of the Tibetan border regions of Nepal.
um, ever heard of tato pani. Of course you dont. you have no idea what you are talking about. Nepalese go to tibet all the time. There is a partially open border crossing for people to go to tibet to shop. They have really cheap pirated DVDs and CDs :-p
Plenty of people go to tibet from nepal it is a standard package tour route.