Yes, but it's still a rather strange statement, at least in my opinion as an ancient historian who digs in the Middle East. It's hardly uncommon for Mesopotamian archaeologists to uncover new temples and palaces, and many are known from texts but have not yet been found. The entire point of conferences like ASOR and ICAANE is the dissemination of new archaeological and historical discoveries.

Perhaps he meant that people believed that the damage to the site from slipshod excavations in the late 1800s and early 1900s and the more recent looting precluded the discovery of more monumental architecture.