Reading history of Tibetan Buddhism, almost all their teachers and concepts were from India. In fact, Bihar has been the biggest contributor to Tibetan Buddhism - the monasteries of Nalanda and Vikramashila gave most Buddhist teachers of central Tibet. Rest from Kashmir/NWFP.
BTW, it is another piece of nonsense that Indians did not travel abroad. They travelled a lot, especially the Buddhist and Hindu teachers. Already [reading history ~1200], I have come across more than a dozen Buddhist teachers from India going to Tibet and teaching there.
In fact, even Nepalese Buddhists routinely got teachers from India-from the same Vikramashila and Nalanda monasteries. In 1100, both were flourishing and producing Buddhist scholars by the ton. So much for `Buddhism died due to Hinduism in India' theories. cc @SVOjha @SAnsumali
E UP-Bihar was clearly a strong centre of Buddhist scholarship in 1100, just as it was for centuries. It will be interesting if we find any references to Buddhist scholarship in Nalanda and Vikramashila [or anywhere else in Bihar-Bengal] after the advent of Islam, though.