Actually the reference to when Vulcans returned to space was from an ENT episode. "Little Green Men" has Quark claim the Vulcans still didn't have warp drive as of 1947, but I wouldn't trust him as an authority on Vulcan history, so I go with the ENT figure instead.
According to Memory Alpha, the specific ENT episode is "The Forge." Christopher
, do you remember the specific dialogue off the top of your head? Vulcans not having 2000 years of spacefaring history behind them has long bothered me.