To alert if a file doesn't exist, configure a 'File Availability'
check with notification criteria as 'deleted'. The user will get
notified when any/particular file(depending on configuration) within
the directory is deleted. Make sure to check if the entered directory
path and file name is without typos. The check will go down when matching file delete events occur.
file content check, if the file name configured is the same as the new
file name on disk, the check will go down when the content matches. If
the configured file name is a regular expression, the new file will not
be watched for alerting(even if it matches) as we get the list of file
names matching the regex when the check is initially configured.
If you still feel there is some discrepancy in the alerting behavior please drop an email to email@example.com