Puranas do exist at those times. There are instances where Pandavas quotes from Puranas to prove that their arguments are dharmic.
One such event happens during the discussion regarding Draupadi's marriage.
During the discussion, Drupada, Dhrishtadyumna says that woman marrying more than one man is a sin. At that time Yudhishtira provides information ...
Abrahamic scriptures may not be mentioned explicitly, but the opinion of Vyasa on other scriptures can be inferred,
(All quotes are from Kurma Purana)
Kurma Purana 1.2.54
सर्व लोक विरुद्धं च धर्मं अपि आचरेत न |
One should not follow the Dharma which is against all the people of the world.
Kurma purana1. 12.
O Best of the mountains by means of