By definition, PIE is a reconstructed language, based on some of the earliest records of phonetically-written languages. As such, proto Indo-European is dated back to prehistory.

On top of that, we can't really tell how close PIE was to any actually spoken language. Many linguists consider it no more than a mathematical abstraction made of the commonalities of the different languages, while others maintain that it was a true language spoken by a prehistoric people at some point in time.

Source: took several courses in linguistics back at uni. A good start would be Introduction to Indo-European Linguistics (Oxford Linguistics) by Oswald J. L. Szemerényi