I'm wondering why your quilt slid off, did you back it with a washable satin? I applaud your efforts and the fact you finished a quilt as you go is a wonder to me. I have an unfinished one I started for my middle daughter when she was in Jr. High. She now is grown and has 2 girls of her own, the oldest is 21. I wonder if I will ever finish it. There is always hope.
As for the warmth feature of your quilt, if you are using poly batting that can certainly cause issues, you might consider cotton. Happy stitching.