The most accurate response would be: Their most sacred site was submerged underwater after International Falcon Reservoir was constructed in the 1950s.
This reflects a significant event that directly impacted the Esto'k Gna's ability to preserve their sacred cultural sites and artifacts along the Rio Grande River. While the other options may contain elements of truth or contribute to broader challenges faced by Indigenous groups, the construction of the reservoir led to a tangible loss of their sacred site.