They could have been caught up around 70 c.e.. These verses are definitely speaking of a changing of corrupt mortal humans to incorrupt immortal humans. Then they are speedily snatched up to the spirit realm with Christ. Not modern at all,but plain as the nose on your face,with all due respect.
Sure, maybe they were, but there is no evidence for it. And yes, the modern reading of the rapture is a modern invention. If it were as plain as you say, Christians wouldn't argue so much over it and it would have existed as a concept prior to ~250 years ago.