I think my sister has been stealing my son's Adderall

My sister has been staying here because.... IDK. She was in town and stopped by and hasn't left. We aren't even close to each other. My youngest son(15) has raging ADHD and is on Adderall. My son got back from a dance competition with his team and told me he only had two pills of his medicine left. Which makes no sense because we got a month supply 2 and a half weeks ago. But she showed me the bottle and it's completely empty. And he only had 2 pills in his weekly pill box. My sister had been the acting strange to the last 2 days. Like super energetic. IDK what else to think. I know it wasn't my older two sons. The only person who makes sense is my estranged sister I know nothing about. IDK for sure though.