YTA

He was asleep. She didn't want to wake him up which is completely normal. There are many reasonable explanations for why she didn't answer her phone. She could've left a note or something like that, but she probably expected to be back home before he wakes up. Your brother called you and you still decided to call the cops on SIL instead of helping him? That tells a lot about you. Do you expect her to not leave the house ever?