Where are the golden plates? Did they ever exist at all or was Joseph Smith really a con-man, of which lied about it?
Sola Scriptura means that the Bible is the only infallible rule for theology. We know the Bible to be inerrant.
With every belief that we stand on, we need to always check them out with the Bible in hand, just to make sure they are sound.
Because of the vast amount of churches, now a days, check their doctrines and teachings with the Bible.