Detect an orphan site
To detect orphaned items, use the following syntax:
stsadm -o databaserepair -url http://sharepointsite/ -databasename [name of DB where orphaned site is present]
Delete an orphan site
To delete orphaned items, use the following syntax:
stsadm -o databaserepair -url http://sharepointsite/
For more reference on this http://technet.microsoft.com/en-us/library/cc263282.aspx
Hope this helps someone...