Symbols- Shaking hands can be a symbol of forgiveness, because even though it's not as inviting or warming as a hug it is still a way of calling a truce or saying that there is no problem between the two of you.
This applies for anyone in a long distance relationship, honestly. I have done this many times. I've cried countless nights because of how far away from me he is, but I always know that, eventually, we will see each other again. In this life or the next.