Who receives Fedex mail at Lackland AFB?

My husband is BMT in Lackland, in is starting his third week, I was sent a postcard with his address. I wanted to surprise him with an overnite Fedex envelope with a letter and appropriate pics. So today they told me that no one was available to take the Fedex envelope, it was being delivered around 1030am -11am. They said they will try again to deliver it on Monday, but I was hoping he would receive is 1st piece of mail today to keep him encouraged. Why was no one available, where they at chapel service, was the delivery location to receive this mail close or they were open at that designated time?