The non-event "happened" in 54 AD as Paul himself thought it would. Period! This, with a long line of other Bible passages have been appropriated by modern abusers. Here's the passage and my own translation and notes, which Are part of a new translation of Pau l's letters I'm working on (don't fret I have been schooled for this and have me credentials).
1 Thess 4:15 For this we say to you in the word of the Lord: that we1 who are alive, we who are left at the Lord’s coming, will not precede those who have died; 16 that the Lord himself will descend from heaven with a loud command, with the voice of an archangel, and with the trumpet-blast of God,2 and the dead in Christ will rise first, 17 then we who are alive, who are left, will be snatched up3 together with them in the clouds at the meeting of the Lord in the air;4 and thus we will be with the Lord forever.
1. The use of the 1 st person plural "we" here and in verse 17 clearly displays that Paul believed that he himself would be "one of the living," "one of those who were left standing" at Jesus’ parousia. It was that imminent for Paul, and thus perhaps why the death of some of the Thessalonians were surprising given the shortness of time believed to be left before Jesus was to come.
2. Paul accesses current apocalyptic imagery that would have been available to him through the apocalyptic literature already penned in the first-century or the apocalyptic fervor "in the air." For the latter, see Josephus.
3. The Greek verb ?ρπ?ζω (harpazo) can mean: ‘to take away,’ ‘to catch up,’ or ‘to snatch.’ In Jerome’s Latin translation the verb is raptio, ‘to seize’ or ‘to take,’ whence the modern (mis)appropriation as ‘the rapture.’ What is, however, perhaps more significant is that Paul uses this phrase (or image) for the living. The term was typically used in the Greco-Roman context for mourners to lament how the deceased was "snatched away" by Death. So in a consolatory manner, Paul has combined the fates of the already dead Thessalonians and those who are living—both of whom will be "snatched away" from death! It might be argued, furthermore, that those who are living, those who remain alive at Jesus’ parousia, are nonetheless reckoned already ‘dead’ via the rite of baptism, which has buried them with Christ (see Rom 6:1-5).
4. The image is rather bizarre, but there are precedents in Jewish apocalyptic literature. Those who have been "snatched away" from death are also, in the apocalyptic event, snatched away from the "wrath of God" (5:9) that will presumably scourge the earth.
http://contradictionsinthebible.com/