just where did they, the lay peopple, lay hands on a written copy of scripture????
Jews since Moses have widely circulated manuscripts, letters and public or private notes, as is easily seen in the sheer number of ‘genizahs’ found everywhere in the Jewish world.
That same place these people did.
John 5:39 Ye search the Writings, because ye think in them to have life age-during, and these are they that are testifying concerning me;
And these people
Act 17:11 and these were more noble than those in Thessalonica, they received the word with all readiness of mind, every day examining the Writings whether those things were so;
In the synagogue.
And do you disallow that some of them may have had their own copies?