A 48-year-old man from Mumbai undergoes laparoscopic cholecystectomy for symptomatic cholelithiasis. Intraoperatively, the surgeon identifies a small artery crossing the neck of the gallbladder before entering the cystic fossa. This vessel is not the cystic artery proper. The surgeon ligates what he believes to be the cystic artery, but postoperatively the patient develops bile leak from the gallbladder bed. Imaging confirms an intact cystic duct and artery. Which anatomical variant was most likely encountered?