Hmm, I don't know about the letter bit. I mean, I automatically assumed the second letter was to Martha and Jonathon, but wouldn't it get sent to the farm? Why would Superman give Murray instructions to find the Kents at Clark's apartment? I figured we wouldn't hear about that letter again until the Kents went home.
Not to give anything away - Superman's instructions to Murray would have been to check Clark's place first - since if he didn't come back he knew his parents would show up in Metropolis to check on him and/or pack up his belongings. OR, Murray's instructions were to hand deliver it and before he headed to Kansas, he checked on the whereabouts of Jonathan and Martha - calling the farm, getting an answering machine, and then calling Clark's apartment.
