Re missing Blut Tit egg

[charlie582]

This is my first Bluetits nest box with a camera, but a little worried as when we checked the camera three days ago one of the five egg had disappeared overnight, then this morning there is quiet a few of her feathers scattered around the nest looks like she was attacked by something, I would have thought if she was attacked in the nest she would have abandoned it,which makes me think she was attacked outside the nest and lost her feathers in the nest box, also the remaining four eggs are still there. She has been sitting on the eggs for six days but I have never seen the male which makes me think she is a lone parent.
Any thoughts appreciated.
Thank you