Welcome to the world of differences between scripture and dogma. The Bible leaves a lot of things completely unsaid. Among these is the precise nature of God. The Bible is long enough already without attempting to actually nail this down.
So you’re going to have to clarify exactly what you mean by “verified.” The Catholic doctrine of the Trinity evolved over hundreds of years of debate. You don’t debate something that has strong inherent support. Nobody debates the ascension of Jesus, because it’s right there in the Bible.
Also note that Trinitarian Catholics share like half of their scriptures with non-Trinitarian Christians, and other non-Trinitarian Abrahamic religions, like Islam and Judaism. If it were that verifiable, then they would all believe it too.