There is a record of an Elizabeth Caldwell who traveled from Mexico to the United States on
27 Aug 1956, which is about six months after Ann Elizabeth Caldwell disappeared.
El Paso is on the border of Mexico/Texas. Is it possible she went over the border sometime after arriving in El Paso and then returned
27 Aug 1956 using her middle and last name?
I don't know how stringent the record keeping was in 1956 on border crossings but it would be nice to see an actual record with the age of this Elizabeth Caldwell in 1956. Too bad these records don't show someone crossing from the US to Mexico. I'm sure there's a more detailed record of these border crossings somewhere.
Migration • United States Border Crossings from Mexico to United States, 1903-1957
View attachment 395132
"From 1953 to at least 1957, all arriving aliens at land border ports of entry were counted for statistical purposes except Canadian citizens and British subjects resident in Canada who were admitted for 6 months or less; Mexican citizens who were admitted for 72 hours or less; and returning U.S. residents who had been out of the country for more than 6 months.
Beginning in February 1956, residents returning from stays of less than 6 months in Western Hemisphere countries also were not counted. Because of regulation changes in 1957, returning residents without reentry permits or visas who had been abroad for 1 year or less were not counted."