Writing of acts aside, what about when the events of Acts were occuring?
"Therefore...if it is not in the scriptures...it is not so."
By the way, this is a bogus conclusion from Acts 17:11.
It is the Jews examining the Old Testament and learning how it was fullfilled in the New Testament, to learn that it was true.
Do you suppose that the Books of the Bible were complete at the writing of Acts?
Thus, Acts 17:11 is NOT about Solo Scriptura!