Is receiving an alcoholic beverage as a gift from a friend considered an offense? This friend doesn't know that Muslims don't drink wine.

Praise be to Allah, the Lord of the World; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

If your friend does not know that Muslims do not drink alcohol, then this will be a good opportunity to invite him to Islam and to embrace it.
Here, you may tell him that Islam prohibits drinking wine as a form of protection of the human mind, which is the most honorable faculty of the human being. This, in turn, will prompt his interest in Islam and make him seek for more rulings of this great religion.
However, it is not permitted to accept such a gift whether it is from a Muslim or non-Muslim.
In addition, a Muslim is not allowed to be mild in such matters, especially in case of forbidding what is evil and enjoining what is good.
In this vein, the Prophet (Sallallahu Alaihi wa Sallam) cursed ten people due to their relation with wine: "The one who presser wine, the one for whom it is pressed it, drinker, bearer, the one for whom it is carried, its seller, the one who earns from the sale of it, its buyer, the one for whom it is bought" . [ al-Tirmizi , Abu Dawood and Ibn Majah ].
Allah knows best.