At this time, the Rapture was still a mystery. The disciples during Christ's earthly ministry would not have considered a Rapture. They only knew of the 2nd Coming of Christ to set up the Kingdom. That's why they ask in Acts 1.6 if Christ was going to restore the Kingdom to Israel at that time. So, you are correct. They apostles would not have been asking Christ about an any-moment Rapture. Under the doctrine of Progressive Revelation, the Rapture was revealed to Paul well after Christ return to heaven.