Perhaps you're right, but I don't think so. Radiocarbon dating (that began post WWII) is what got Clovis dates accepted; Leakey's visit was circa 1930.
Leakey didn't do Calico until the late 1960s. Calico didn't even start up until 1964. There were radiocarbon dates in the western US much older, at that point, than 3,000 years.