On the home screen, assuming you're still using stock SenseUI, press:
Menu-> Accounts & Sync-> Tap 'Sync all' at the bottom.
If this doesn't restore all your contacts, you may have signed in with the wrong google account, if you have more than one, in which case just tap the google account in the sync menu, then hit 'Remove account' and sign in with the correct one. Respond A.S.A.P. so we can get your phone working again as fast as possible!
