e2.fsck: Root inode is not a directory. Clear?

Yeah, kill the root directory! It is FUN, isn't it?!

glostykiss: ext4 lost+found sort pain-killer

It is an extremely simple file indexer.

go get github.com/derlaft/glostykiss
Usage is as simple as glostykiss /mnt/lost+found /tmp/database.sqlite.
You will need <magic.h> (libmagic-dev package in Debian-like distros, file-devel in OpenSUSE).
This will create a sqlite3 database with a file index.
Each file and directory in lost+found will be presented in files table.
For each file without an extension (i.e. files without a dot in the name) will have a type column filled with a mime type obtained by libmagic.
Use any SQL-queries to find the stuff you need over thousands of unnamed files.
You can query the database even when the index process is not yet finished.