I agree with Patrice. We really don't know how it came to be there. One possibility is that the person making it had something happen to him or her. That would explain the basting threads being still in it.
It was hard when I found my mother's last knitting project in her house - she made hats for a cancer unit. She had only just started that hat and I had to unravel it and give the yarn away - to Goodwill. I couldn't stand to keep it.
lots2do