PIE is, exactly, the name of that ancestral language. We are able to deduce many details of that language from a large amount of distributed evidence about extant languages and extinct written languages. A great many details have been elucidated from this evidence, more all the time.

It is hard to understand what you think is the difference between the ancestral language and PIE. PIE was almost certainly not a written language, so carvings or manuscripts can exist only in fantasies. We have enormous evidence of the existence of non-written languages.