What does "They met a while back." mean in English for Spanish?

In English for Spanish, "They met a while back." means:

Se conocieron hace un tiempo.

Listen to "They met a while back.": (If you have an HTML5 enabled browser, you can listen to the native audio below)

This is a phrase that is used in the GamesForLanguage English for Spanish Language Game in the following scenes:

• English for Spanish 4, Level 1, Scene 5