Before she waded into the water to take a holy dip among the teeming throngs at the world’s largest religious gathering, Draupadi Devi reached into her blouse and handed her husband a small pouch to safeguard.

Inside was a slip of paper with his phone number scrawled on it, so she would have it if they got separated in the tangle of limbs and luggage that is the Kumbh Mela, a Hindu festival held every three years in one of four cities in India.

This year’s version of the event is being called a Maha Kumbh, or Great Kumbh, because it coincides with a celestial alignment that takes place only every 144 years. So the multitude of pilgrims, devotees, seers and ascetics is even bigger than usual — and even easier to get lost in.

After her bath, as they made their way through the crowds, Ms. Devi lost sight of her husband, Umesh Singh. Gone, with him, was her pouch.

Confused and scared, Ms. Devi, 65, wound up at the festival’s lost-and-found center, part of the immense temporary infrastructure that attends to the faithful’s earthly needs as they perform rituals intended to purify the soul.