Keyer is not in the effects panel

FWIW, on 10.7.1 the Keying and Masks are grouped under the same category, now called "Masks and Keying", and the "Keyer" was renamed "Green Screen Keyer":

Make sure you're looking in the correct place.

If the Keyers really aren't there, you could first try resetting FCP preferences (hold option and command while launching FCP) to see if that helps. Don't forget to change your prefs back to the way you like (disable background rendering, etc.)

the keyer is missing

Where are you looking? Please show me a screenshot.