After the incident in the slums Uriel struggled to find a way to fulfill his oath. Truth be told, he wasn't expecting to find answers anytime soon soon, but he somewhat knew what steps he needed to take in order to find out more about the ancient people. He needed to enter a dungeon to learn more about them, but the only one he knew was the one located beneath the Alamo.
Unfortunately for him, losing David Crockett's diary was a huge setback for his investigation, but not everything was lost. Even if the Texians lived in San Antonio when the Alamo was built, the Comanche lived there long before them. This meant that the dungeon beneath the Alamo would most likely be related to the Comanche rather than the Texians.
Uriel figured what the Texians did was akin to the Mexicans building a fort on top of Chichén Itzá. Texans and Texians most likely found the landmark that signaled the entrance to the dungeon and built the mission of San Antonio de Valero on top of it.
