Crying but Silent

Last night, I awoke to a crying baby, it was AJ.  He was in his room really crying.  I went to his room and opened the door to find my almost two-year-old crying his eyes out and holding his pillow just standing at the door waiting for me to come.  Once the door was open, he walked passed me, down the hall, through the living room, through the kitchen, and into the computer room, where he stopped to stare at the computer chair his daddy would normally be sitting in, that is if it wasn't the middle of the night.  He continued to cry and I knew this would end up being a rocking session in the recliner, so I got one of his sippy cups and filled it with milk, knowing what was coming next.  When the refrigerator door closed, he was beside me reaching for his cup.  I handed it to him and walked back towards the living room to turn the TV on get ready to rock him.  The crying stopped, so I turned around to see he was walking and drinking.  Walking right passed me, walking through the living room, down the hall, into his room, and climbed back up in bed.  Now, I know he doesn't need a cup in bed, but it was 4 am and he was happily going back to bed, although he never uttered a word, not that he can talk very much anyway, but I mean it was a bunch of crying and then silence.  It was over before I knew it and I still have no idea what had him so upset.  Ah, my life.