It is sad that your friend could not show you where it was in the bible. Here it is:
1 Cor 15
50Now this I say, brethren, that flesh and blood cannot inherit the kingdom of God; neither doth corruption inherit incorruption.
51Behold, I shew you a mystery; We shall not all sleep, but we shall all be changed,
52In a moment, in the twinkling of an eye, at the last trump: for the trumpet shall sound, and the dead shall be raised incorruptible, and we shall be changed.
53For this corruptible must put on incorruption, and this mortal
must put on immortality.
54So when this corruptible shall have put on incorruption, and this mortal shall have put on immortality, then shall be brought to pass the saying that is written, Death is swallowed up in victory.
55O death, where
is thy sting? O grave, where
is thy victory?
56The sting of death
is sin; and the strength of sin
is the law.
57But thanks
be to God, which giveth us the victory through our Lord Jesus Christ.
And also:
1 Thess 4
13But I would not have you to be ignorant, brethren, concerning them which are asleep, that ye sorrow not, even as others which have no hope.
14For if we believe that Jesus died and rose again, even so them also which sleep in Jesus will God bring with him.
15For this we say unto you by the word of the Lord, that we which are alive
and remain unto the coming of the Lord shall not prevent them which are asleep.
16For the Lord himself shall descend from heaven with a shout, with the voice of the archangel, and with the trump of God: and the dead in Christ shall rise first:
17Then we which are alive
and remain shall be caught up together with them in the clouds, to meet the Lord in the air: and so shall we ever be with the Lord.
18Wherefore comfort one another with these words.
As you can clearly read there is going to be a time in the future when there will be a particular generation of believers who will not die but while alive will be changed to a glorified immortal state equal to that of those who are resurrected from the dead.
This is called the rapture because it is the English word of a Latin word from the Greek word that was translated "caught up" in the text above. So if you or any of your friends are offended by the word "rapture" Then just read both of these passages without taking a breath, and then they will finally understand why a using a single word is so much more convenient. LOL
Of course reading both passages is important to educate those who are unaware of this topic, but once both passages are read and understood, it then becomes convient to refer to this EVENT as the rapture, providing your audience knows what passage we are referring to.
Now that this EVENT explained in 1 Cor 15 and 1 Thess 4 will occur is not up for debate. Therefore one should not say they do not believe in the rapture. That is like saying they do not believe that Paul was telling the truth. It is usually the timing of the rapture that is in question. Some believe that the rapture will occur before the Great Tribulation and the wrath of God is poured out as described beginning about Rev 6 forward. Some believe that the rapture occurs in the middle of the tribulation and some believe that the rapture occurs at the end of the tribulation but most evangelicals believe in the event occurring at some point when the Lord Returns and there will be a people alive at that time who WILL NOT SEE DEATH. They will be changed in the twinkling of an eye and be given the same kind of immortal bodies as those who did die and are resurrected. This EVENT WILL OCCUR. It is the blessed hope of the saints and should be preached and used to comfort one another as we wait for his appearing which will mean the glorification of our bodies and our gathering to be with Him.