Separation Anxiety??

....  Have we possibly seen the beginnings of this so called separation anxiety that occurs around six months of age??  I'm not sure...  Yesterday, as I was sitting him in his highchair to let him further master his sippy cup of water, he cried like no other!  We had just played and played, changed a diaper, rolled around happily, even laughing if I remember right....I set him in his chair, with toys of course, and the beloved sippy cup, and he burst into tears!  He was super sad, but still reaching for his sippy cup.  So I ran up to him put my hands on his cheek, and he stopped and smiled at me.  I tested my theory again by walking away...TEARS.... came back... HAPPY... Who knows?? Either way, it's something my mom told me I should put in his baby book?...So here I write...