ISB ~ 2 Peter 3 v15

Paul wrote to you:The recipients of 2 Peter were also among the recipients of at least one Pauline epistle. It could be a letter now lost (like the one mentioned in 1 Cor 5:9) but is more likely a letter in the NT canon. If the previous letter implied in 2 Pet 3:1 is 1 Peter, an epistle written to believers in Asia Minor, then the list of candidates can be reduced to Galatians and possibly Ephesians and Colossians, each of which was written to congregations in Asia Minor.