I agree 100%. When I'm depressed 99% of the time I want to be left alone so I can clear my head and think for a little while. When/If I feel like I need someone to talk to then I will call them and hope they can provide some sort of support. I too have recently lost my closest friend of 8 years due partly to this behavior. But like you mentioned, a real friend or loved/cared about me would understand. In the end, I have come to realize it wasn't worth it.

But to answer the original question, I can say that 90% of the time they WILL come back. They just need some time to think about everything that had happened or that's going on around them. The person who is having issues might always push people away to avoid a yelling match or might be fearful of saying something they really don't mean but said it out of anger/frustration.