My T has offered a hug twice. The second time was similar to your situation. I was leaving and she just stopped me and offered a hug. I wasn't real comfortable with it and I hugged her with one arm. She realized that she had made me uncomfortable and mentioned it in the next session. My guess is you can either initiate by asking or hint that you feel like you need a hug. T would probably offer one then. However, I think the initiation is better because it might give you a chance to practice assertiveness. I have major trouble asking for anything from T. So, I keep thinking about asking for something just to test the new behavior of asking for what I need from T. If you look at it that way, even a "no" response can be okey. But, I suspect your T will go for it if you express your desire for a hug.