Recovering a PI tag that was deleted accidently is extremly annoying.
Why do I have to create a new tag and reprocess all historical archives to convert the old tag to the new tag in the archives? (https://techsupport.osisoft.com/Troubleshooting/KB/2651OSI8/)

It should be quite easy to just recreate the original tag if you have the pointid and recno. Maybe when deleting a tag you should only mark the tag as deleted instead of removing it from the pi point table.