Vlingo is designed to keep in sync with your address book at all times. On rare occasions, this may not happen, and you'll see a 'No Match' even when the person's name is spelled perfectly in Vlingo's text box. Alternatively, you may be able to find the person's name but it will show up without a phone number or email address.
If you suspect this situation has occurred, go to Vlingo -> Help and type ML. There is no input box to enter this in, just bring up your BlackBerry's keyboard and type ML.
Then click Rebuild Address Book. Give it a few minutes for everything to stabilize. Then try using Vlingo again.