As is well known, the Pali canon was first written down in the Alu Vihara monastery in sri Lanka, around 20 BCE. This is based on an account in the Mahavamsa, which is generally reliable as far as historical details go.
The original text copied 2,000 years has long vanished in the mists of history. Manuscripts in Sri Lanka generally do not last longer than a few hundred years, and presumably it would have been re-copied multiple times. The Alu Vihara, it seems, remained a center for preserving manuscripts. Sadly, though, the old library was destroyed, along with any manuscripts, during the Matale rebellion of 1848. So we shall never know exactly what was in it at that time.
We do know, however, that the Sri Lankan Sangha requested that manuscripts be imported from Myanmar and Thailand during the colonial period, due to the widespread destruction of the local manuscripts and difficulty of sponsoring new copies. Obviously this request would not have been made if complete and pristine ancient copies existed at a well-known temple like the Alu Vihara.
This is why we are currently engaged in a project to record and digitize the oldest recognized Sri Lankan manuscript, the Dutiyaparakkamabahu Cullavagga housed in the national Museum of Colombo. Again, if ancient original manuscripts existed there would be no need for this.
Despite all this, it is a common belief among Sri Lankans that the Alu Vihara original Tipitaka still exists. In fact, many people seem to be surprised to hear anything different. I think the story is simply circulated saying that the Pali was written down, and no-one thinks any more about it, and if they do, they assume it’s still there.
Some people get quite attached to this idea, and insist that it is really true. To which I say, great! Please take the scenic and delightful drive an hour north of Kandy to Alu Vihara, and snap a few photos of this ancient manuscript on your phone. You will have single-handedly made the greatest contribution of Sri Lankan archeology to world culture: the confirmation of a genuine Tripitaka dated only a few hundred years after the Buddha! This would be the greatest revolution in Buddhist studies in a century!
Unfortunately, this won’t happen because of the whole “not being real” problem. This is why we have scholars who do the hard work of researching these things and reporting on the facts. If you’d like to know more about the story of manuscripts in Sri Lanka, read Ven Ñāṇatusita’s excellent essay on the topic.