Think my kid's dad is doing drugs again

My boys moved in with their dad back in August because they were not getting along with my husband and my oldest son and husband got into a right with each other and they broke my table fighting. They've never gotten along with my husband. U haven't spoken to my kid's in 3 months because we got into a fight over my husband and they said they hated me and they are happier with their dad. Their dad is a recovering addict. They are in Kansas with their dad and I live in Arkansas. Their dads sister reached out to me to ask if my kid's dad was back on drugs and I said I would hope not and why and she said she saw him at work and he was clearly going through withdrawal. He works at a hospital as a custodian and she was there to see a friend and he was sweating and she saw him throw up in the trash can he was using. He was just clearly going through withdrawal. And my kids are down there but mad at me.