When Twitter originally launched, it offered an integrated, basic directory search function. For one reason or another, it vanished over night. It was a disappointing move as I, like many, relied on search to catch up with friends that we knew were on Twitter, but we were all too busy to remember the IDs, let alone add them to our email signatures and business cards for future reference. TwitDir is one of the many cool third party apps that reintroduces…