Where do you see Thomas or in the immediate context that the Father is included when He/Thomas specifically said to Jesus Christ Himself, "My Lord and my God." Thomas is "NOT" including the Father just because you say so. And when you said, "Because Jesus says that his Father did not leave him alone," Jesus was talking about Him going to the cross at John 16:32, "Behold, an hour is coming and has already come, for you to be scattered each to his own home, and to leave Me alone; and yet I am not alone, because the Father is with Me."
This is a completely different context dagallen and has nothing to do with what Thomas stated. In fact, look at 2 Corinthians 5:19, again referring to the cross, "namely, that God was in Christ reconciling the world to Himself." In other words, Christ was never without the Father from birth to death which means your explanation is "moot."
PS: If Jesus had said"I am God" would you believe Him, yes or not?
IN GOD THE SON,
bluto