The event is generates an error and the log shows the reason why, but the log also seems incorrect. The log displays the following:

"called with invalid record reference" , "the record may have been deleted".

2011-11-17 07:15:31 (365) worker.4 worker.4 Connected
2011-11-17 07:15:31 (374) worker.4 worker.4 Processing 0 emails
2011-11-17 07:15:31 (374) worker.4 worker.4 Processing email total: 0, new: 0, deleted: 0, unread: 0
2011-11-17 07:15:31 (397) worker.0 worker.0 WARNING *** WARNING *** EventRecord: getEventTarget() called with invalid record reference: sc_request.d63e4f07299a148044d78d67c8138c5e for event: email_equipment_return, could have been deleted
2011-11-17 07:15:31 (423) worker.4 worker.4 Processed 0 emails

The record is there and is not deleted. There are events that do not have a state of "error" that call to the same record type in the same way.

1. View the events for errors and get the sys_id of the record in the URI field of the event.
2. Go in to the daily log for the same day of the error and search by the sys_id.

Note that the the log says a record does not exist when it actually does.