Lost Patches in Upgrade

I was recently working on an upgrade of the cluster from 11g - 12c and ended up in a peculiar situation.
The ora inventory did not get updated but the patches were applied.

The solution was finally found in an undocumented utility in Oracle Home kfod.

Use the command kfod op=patches

[grid@host1 ~]$ /u01/app/12.1.0.2/grid/bin/kfod op=patches
List of Patches
===============
20243804
20415006
20594149
20788771
20950328

Now if you ever end up in a situation like this and want to be sure if the patch was installed or not by looking at the home and not just the inventory xml, you can use this trick.

The best way in such situation is to rollback, the rollback procedure is what you are aware of, however since the inventory is not updated opatch might fail.

I will see if I can post a blog to handle such a situation, but for now if you install a superseded patch that should do the trick.