Praise be to Allah, and may Allah’s peace and blessings be upon the Messenger of Allah, his family and his companions.
As to what follows:
I do not think that is permissible, because it is well known that the Mus’haf is an endowment for the mosque. What has been agreed upon by the scholars is that the principle is that it is not permissible to sale property that has been given as waqf if no benefit can be derived from it and there is no probable benefit in its selling. This exchange in question is a type of sale because selling is exchanging property with property. Therefore it is obligatory that you return the Mus’haf you took.
And Allah knows best.
Your brother,
Dr. Khalid al-Muslih
13 / 11 / 1424 AH