If you're not sure you've seen an incident, report it anyway.
Most security folks (and IT folks, for that matter) would rather hear about a problem from you than to figure it out afterwards while troubleshooting a system failure. If a phone call from User Support doesn't sound quite right, if a common email announcement is just a little off, or if a caller on the phone is too stressed to remember his or her password — don't be pressured and don't be rushed. Rush and pressure are among the "social engineering" hacker's best tools. Ask for help! Call your supervisor, call your IT group, and call your InfoSec group on the spot for assistance. You are as responsible (or more) to the whole company as you are to the one person on the phone! Don't let one person's stress jeopardize the organization's information security.