Of course it is, right in 1 Thessalonians 4:15-17. No one disputes this. But this refers to Christ's Second Coming, not to a separate, secret event where Christ comes twice--after the tribulation and again after an earthly 1000 year reign. It does not say that in Thessalonians and one has to cobble together a body of unrelated verses from all over the Bible to build a whole body of novel theology unimagined to 1800 years of Christianity.
Yeah, real *secret* when millions of people disappear.
Honestly, this idea that the rapture is *secret* is garbage beginning to end.