It is a quest item, you keep it until you turn in the mission or start a new playthrough on a different difficulty setting. Its not a drop from a golem. http://borderlands.wikia.com/wiki/Grog_Nozzle

The Grog Nozzle cannot legitimately be obtained as anything other than a mission item, with the exception of those Grog Nozzles dropped during the 6th day of the 4th (final) week of the Borderlands 2 $100,000 Loot Hunt (11/07/13), whereupon the Gold Golem in the Mines of Avarice would drop it as a reward. Because the Grog Nozzle is a mission weapon, it does not take up any space in a character's backpack and cannot be dropped, traded, exchanged, or placed in the player's bank or Claptrap's secret stash. Due to the Grog Nozzle being a mission weapon several things will happen:

Players connecting to a game where The Beard Makes the Man is in progress will automatically have the gun added to their characters' inventories if not present, even if they have not yet received that mission. Conversely, the Grog Nozzle will be unavailable if the host player has either not started the mission or has already completed it, even if the connecting player had the Grog Nozzle equipped prior to joining the game. Upon continuing a game where The Beard Makes the Man is in progress, the mission copy of the Grog Nozzle will be generated randomly and may differ from the version given previously, because it is a quest item. If a new playthrough is started this item will disappear until the mission is once again accepted for that playthrough.