Why do we say that the Mushaf of ibn Mas'ud is LOST? while we have some (?) variant

Salam, in Kitab al-Masahif of Ibn Abi Dawood the author provids some variant quotes of the Mushaf of ibn Mas'ud. I also heard that we have some (other) quotes in tafsir books. Can we make the whole Mushaf of ibn Mas'ud today or are there some missing parts and that's why everyone claims it's lost? or maybe we have conflicting hadeeth about the same verse. I dont understand. Thanks you