He and the chief railroad inspector scoured the city, saying they were searching for a lost railroad employee; there was no lost employee, and in fact the employee they said was lost never existed. The ruse gave Butler access to various areas of the city. In the process of the so-called search, they located weapons in use by the Mexican army and determined the size of units and states of readiness. They updated maps and verified the railroad lines for use in an impending US invasion.