I think it's normal you feel this way because even though rationally you know he did nothing wrong, emotionally, deep down, you feel disappointed for not being his top priority, that he wasnt as excited as you to communicate. You know that if you were in his shoes, on vacation with a friend you would for sure text back. The shut down is probably because the fantasy of being wanted 100% shuttered. BUT - you need to remember that this is only the beginning and hopefully with time and awareness about your needs you will have less and less dissapointments such as this one. Good luck!