Hmmm...are you sure you're in the same context and room that I'm in? :-)
“Hmmm...are you sure you’re in the same context and room that I’m in? :-)”
The context is appearances after the resurrection but before the ascension. Jesus is explaining to Mary what he means by the reference to “God”. Thomas is not there in the same room when Jesus says, “but go to my brethren, and say unto them, I ascend unto my Father, and your Father; and [to] my God, and your God.
Thomas was not at any of the appearances of the Lord before the confrontation in John 20:19 so he did not know what Jesus had said about the Father.