Call or email, leave a message asking to be called back IFF the candidate was exceptionally strong. Assuming you aren't a competitor, you'll probably get a call back if true. If the guy was meh, it is a nice way to pocket veto.

For when you do employee referrals, if employees are getting pressured by lames to refer them, let them do no-op referrals. Default bring meaningless, and "strong referral" being a real referral. Google, Facebook, etc do this.