A few days ago I was just grazing through a copy of mine the, Septuagint LXX and I ran into an interesting section. Psalm 83:18...there is no such verse. If anything the verses stop at verse 15. It seems that this verse, along with 1John 5:7, went the same way.
And the Witnesses are always showing us in christiadim that Jehovah is in verse 18...yet no verse is found.
How was a verse which was never in the Septuagint found its way into the Bible? Consider 1 John 5:7 for referense.