Odd EM Event; Only Clear Notice is Received - How do I trace the entire Event?

Hi EM Experts

I have a 10.2.0.4, single instance database running on AIX 5.  It is monitored by a 12.1.0.3 EM agent.  Enterprise Manager is 12.1.0.3 running on Red Hat 5.

Starting a few weeks ago, EM sends a daily "clear" alert with the message "Tablespace TEMP is 0 percent full".  I have other 10.2 databases on AIX, and only this database is the subject of these clear messages.  The metric is Tablespace Space Used (%).

I don't see any alerts or incidents raised on the TEMP tablespace for the database, just the clear notification.  How do I trace the entire event?  I'd like to know why it happens and how to stop it.  For the record, clients do not use the TEMP tablespace.  There are custom temporary tablespaces set up for clients.