They saw that the Kusha grass on which the Ambrosia had been placed was empty. It had been taken away by a counter act of deception.
यत्रैतदमृतं चापि स्थापितं कुशसंस्तरे। तद्विज्ञाय हृतं सर्पाः प्रतिमाया कृतं च तत्॥