Does my leaving Arafat for a short time to buy water, then returning before the sun sets, while being unaware of the ruling and it being my first Hajj, affect my Hajj?

The time for standing at Arafat begins from the declination of the sun on the ninth day and extends until the dawn of the Day of Sacrifice (Yawm al-Nahr). Whoever stands at any part of this time has observed Arafat. The proof for this is the saying of the Prophet, peace and blessings be upon him: "Whoever witnesses our prayer with us and stands with us until we depart, and had stood at Arafat before that, whether by night or day, his Hajj is complete and he has fulfilled his purification." The majority of scholars hold that whoever stands during the day must extend the standing to include a part of the night, and whoever fails to do so must offer a sacrifice (dam). Departing from Arafat and then returning to it does no harm, and all of Arafat is a place for standing.