I would not be concerned with whether the man of sin is 'mentioned' in Revelation as much as why you can't see it.
Revelation 13:5
And there was given unto him a mouth speaking great things and blasphemies; and power was given unto him to continue forty and two months.
Revelation 13:6
And he opened his mouth in blasphemy against God, to blaspheme his name, and his tabernacle, and them that dwell in heaven.
Revelation 13:7
And it was given unto him to make war with the saints, and to overcome them: and power was given him over all kindreds, and tongues, and nations.
Revelation 13:8
And all that dwell upon the earth shall worship him, whose names are not written in the book of life of the Lamb slain from the foundation of the world.
Revelation 13:9
If any man have an ear, let him hear.
That was to a church that will be spared from the Tribulation wrath apparently. What they did got them a blessing, but that is not salvation being talked about. It is the blessing of being spared from the Tribulation (Raptured) as far as I can tell.