The winds of change are blowing

We found out today that the b-i-g's teacher is out on medical leave and the school is looking to hire someone new. The grownup part of me is like Yeah, take care of yourself, this is just a job and your health and the life of your children is something to manage first. but the mama part of me, the mother bear, feels like someone has died. Not someone close. I am not heaving and bawling and overwhelmed but just so sad. So disappointed. So...i do not have words to describe it. And how do you explain (rhetorical) to a 5 year old that his teacher is leaving and never coming back when for weeks, even before he knew her, we in all honesty and faith, assured him that his teacher would love him and nurture him and that he is to respect her and on and on and on and now, 6 weeks in to his first school experience, she is gone. How do you explain that or anticipate the needs? I just don't know and I feel so sad about it. I can only hope that her replacement will be just like her because she was perfect for him and for us. So calm and nurturing, encouraging and sensitive to her students and their individual personalities. How will anyone else compare? I can't even anticipate the answer for myself, much less him.
And so, tomorrow we go to school and meet the SUBSTITUTE teacher and then we meet the REAL teacher who knows when and what if she is mean, or not in control??? I just feel the heavy uncertainty of change and I do not like it. And I am helpless to alter this HUGE detail of my child's life and that just does not feel right. Or good. But I am even helpless to change even that. I can't homeschool. Not the way I think it should be done. Too many littles. Too much laundry. What's a mama to do?