There are some things that can cause a decompile process to fail completely, such as wack complex geometry, but nothing is impossible for an proficient to senior mapper, let alone an expert, in terms of recreation from ground up. Usually an recreation ends up being better than the original in some way.
But it would be nice to ask the person who made it for sharing their source data and for an mapper about to quit his hobby to share his projects sources to enrich the community with those valuable resources. - Just like Skals shared his projects sources with me when he quit Gold Source.
For Skals-sama