Thanks for the replies.
I should have included that:
a) We do have SNMP traps configured and verified (we have been using the SNMP alerts for some time). (re: reply #1).
b) The alarm was triggered from 3 Hosts. (re: reply #2).

c) Our SNMP server/listener does not seem to have received this specific trap.
Thus I sought some help to understand my problem. I was trying to confirm: that vCenter "should" have sent the trap. In this case I need to confirm it was received by the SNMP server and somehow "lost".
Thank-you,
Luis