After further study, I found the missing command. To add Open Containing Folder to the general context menu using regedit, navigate to HKey_Classes_Root/*/shell and create a new key with any name. Set the default value to Open Containing Folder. Under the new key, create another new key with the name "Command". Set the default value to "explorer /select,%1". With this modification, the containing folder of any file can be opened on righit-click, including items found using the search utility.