If the Big Bang is the same event as God speaking the heavens and the earth into existence, I don’t think any Christian theologian would reject it.
That 'stuff' is still around, though tremendously diluted per unit volume due to the expansion and thus cooling of the Universe. There is no indication --that I can find so far-- in The Bible which tells us precisely when the dimension of Consciousness or the dimension of Spirit was added to the Universe of God's Creating.
For planet Earth and humankind, the Bible indicates that dimension Spirit was added to the mix with God Breathing a living soul into Adam, as more than just a soul of consciousness.