I was researching references to the trinity in scripture, and although I am aware that the reference in 1 John 5:7 is likely spurious, can't seem to find the verse in the NRSV. There is no note as to why, but most bible translations I am familiar with have some version of 2 Cor. 13:14 without notation (NIV, NKJV, ESV, NASB...). Perhaps the texts on which the NRSV translation rely do not include it while the other translations have some that do, or perhaps it is considered spurious on the basis of its similarity to 1 John 5:7. Why is this verse excluded only in the NRSV?
There is no text missing from the NRSV.
It is simply a slightly different verse numbering. The NRSV text reads:
12 Greet one another with a holy kiss. All the saints greet you. 13 The grace of the Lord Jesus Christ, the love of God, and the communion of the Holy Spirit be with all of you.
The NIV, by comparison, reads:
12 Greet one another with a holy kiss. 13 All God’s people here send their greetings. 14 May the grace of the Lord Jesus Christ, and the love of God, and the fellowship of the Holy Spirit be with you all.
The NKJV reads
12 Greet one another with a holy kiss. 13 All the saints greet you. 14 The grace of the Lord Jesus Christ, and the love of God, and the communion of the Holy Spirit be with you all.
The NRSV has simply run verses 12 and 13 together as verse 12 and renumbered verse 14 as 13.
The verse numberings are not part of the original text and not considered "inspired", though they are standard in most translations.