Some background about my question, I have a Muslim friend who really loves and studies theology and when discussing Christianity. He asked me how there seems to be incongruencies and he pointed out 1 Thessalonians 4 and so I replied to him that Paul had actually mentioned and explained what He by in 1 Thessalonians and had rectified it in 2 Thessalonians, but He said that according to known biblical scholars 2 Thessalonians was not written by Paul himself but others which we seen continued to argue about because I kept saying that even if it wasn't Paul himself who wrote it, it was someone really close to Him.

Now, I really wanted to hear someone the perspective of someone who is well versed on the bible to explain to me this disjoint. Was Paul just being hopeful and when the Second Coming was but that He was only hopeful? 

Why is it mentioned in 1 Thessalonians 4, “According to the Lord’s word, we tell you that we who are still alive, who are left until the coming of the Lord, will certainly not precede those who have fallen asleep. For the Lord himself will come down from heaven, with a loud command, with the voice of the archangel and with the trumpet call of God, and the dead in Christ will rise first. After that, we who are still alive and are left will be caught up together with them in the clouds to meet the Lord in the air. And so we will be with the Lord forever. [1 Thessalonians 4:15-17]” but it didn't seem that this was what had happened during the time of Paul?