DoubleH,
Like every other thing in computer, especially unix, there could be thousand and one reasons that may have caused the sudden file disappearance, that include but not limited to user error and malicious code being introduced purposely or mistakenly. Haven't said that, you need to roleup your sleeves and pull out your good old investigative skill and start combing your entire file system/utility scripts.
1) You can start with the crontab ( crontab -l ) , make sure there are no strange entry you did not put-in or not aware of. Or a possible typographical error that may have pointed a well intended clean-up script to a wrong dir - such as the "/opt/loca/bin"
2) Check each of the scripts listed by the crontab -l to ensure none is deleting a wrong file
3) Check your file system for sudden unexplainable increase in size, that could indicate a possible attack.
My guess it that you must have check your dmesg (/var/adm/messages) , if not you may want to do that first, it could hold the missing link to the mistery.
I hope this and other contributions from other members of the forum will help you in unraveling the mistery.
goodluck. ^^^^^^^^^^^^^^^^^^^^^^^^^^
Experience is the Best Teacher
But its' cost is Heavy!
^^^^^^^^^^^^^^^^^^^^^^^^^^