What is Eds teacher doing in chapter 14 of Fullmetal Alchemist?

There hasn't been an explanation of what they were doing there, specifically, but it's implied later in chapter 20 that that trip to Central City was the very same trip where they met Van Hohenheim.

From chapter 20:
Sig: "Come to think of it, on our travels at Central City, we met an alchemist who was really into stones."
Izumi: "Oh that man! That's it... I think his name was Hohenheim."