I think that "number's come up" means that John was drafted, and sent to Kuala Lumpur, and Caroline at some point tries to contact him, but "somebody stationed" there says "he thought you went out" meaning that John is probably out cavorting with local women, or at least that's what Caroline is probably thinking at this point.
I think that "number's come up" means that John was drafted, and sent to Kuala Lumpur, and Caroline at some point tries to contact him, but "somebody stationed" there says "he thought you went out" meaning that John is probably out cavorting with local women, or at least that's what Caroline is probably thinking at this point.