Well, that is understandable. Basically, you want two things: 1) His support of your doing research, and, 2) His missing you.

You got one and not the other, so you are sad and depressed.

The good thing is that he is supportive. I think this is great. But it is disconcerting that he appears indifferent with regards to the length of your stay in another state.

So you are well within your right to be a little unhappy.