Mama's Please Read/Vent. How Would You Feel?

In the summers my husband and I work June and July mornings 7-3pm. My aunt watched Jr which (who will be 1 on Friday) for 4 weeks then my sister has had him watching him during the day the remainder. She has a daughter that just turned 13 just a month ago and a 5 yr old boy that is wild. My sister never had problems leaving her kids at home alone, me personally ALWAYS had a problem hearing that they were there alone, even when they was like 10 and 2yrs old, bc ANYTHING can happen. Well I got a call yesterday from my sister saying tell your husband the baby was sleeping and I didn't want to wake him, my husband is taking me to school and going to pay bills, Jr is at home with the kids. I FLIPPED! A 12/13 yr old is not capable of caring for a baby! She dont know what to do if he chokes, if he stops breathing, if he falls, if she is playing with him and hurts him by mistake! On top of it she is left with no phone?!?!!? I was so upset, she could have called my husband THAT WORKS not even 5 mins away to get off 30 mins early just to come get him! Or even called me bc I was getting off work across town and I could have just drove over to be with them. The thing is she thinks it is fine and I am not okay with it at all, just the thought of my baby, my first little baby boy no longer being here bc of ignorance on my sisters part just kills me. The fact she called me after she left also, without calling me to ask me or letting me know b4 hand drives me insane.... How would you all feel?!?!?!?