With the Navtree folders it's a physical deletion versus a logical one. This means that if you take a look at the xtk:folders schema you won't see any @isDeleted field or anything that allows the folder to only be marked as deleted and recovered.
That means when you accidentally deleted the folder it was completed wiped from the database. Jon's previous suggestion was basically just recreating the deleted folder from scratch versus recovering the original. If you want the sub-folders you'll have to create those too.
Unfortunately however there isn't anyway to recover the originally deleted folder and sub-folders outside of a database restore from a backup prior to the deletion.