AITA for not getting my son his phone back because he gave it to my sister when he got fully naked in front of her.

My son, 15, got into a fight with his ex girlfriend and she dumped him. Some days later, he told me he wanted to get her back. I told him to give her space. He asked me what if my sister, 30, was going to be his girlfriend. I told him it would never happen even if he was the last man in the world. He was frustrated and he asked my sister. She turned him down although she was very flattered. Some days later, he cut his hair short and buzzed all the hair on his head off. He was arranging his bookshelf and he fell and broke the bookshelf on himself. He went to get food with me and he dropped his tray. We were in the car, he spilled soda on himself. Literally anything he does, he does it wrong. He was driving me crazy. So one day he asked me if he could talk to my sister again. I told him it was not going to happen. So he told me if you won't talk to me then at least talk to my sister. I was angry and I told him I am not your father I am your mom and she said she was flattered but you're too young now. He asked her and she turned him down too. He told us both he would kill himself if he didn't get a girlfriend. My sister told him that he could have her for a day if he does what she says. He agreed and she told him to go on a date with her and if he didn't do anything embarrassing she might give him a chance. He went with her on the date and she asked him to get her the menu. He stood up and his pants fell. So they left the restaurant. She took him to the park and he tried to sit and his pants fell again. She took him to the mall and he got into a fight with a guy over who was going to sit in the chair first. So they left the mall and she said she was definitely not going to give him a chance. It was getting dark so they went to her house. She went to change and she was walking through the hallway in her underwear when my son was walking out of the kitchen with no clothes on. Literally naked. Now my sister just changed and had no clothes on. My son and my sister were both in their underwear and my son was walking out of the kitchen with no clothes on. She told him to put some clothes on. He told her he was going to kill himself if she didn't go out with him. She told him the only way she would be his girlfriend is if he gave her his phone. He gave her his phone. So now I won't give him his phone back. He kept asking me to get him his phone and I told him no. He asked me why and I told him it's because you got naked in front of my sister. He told me he took a shower. I told him that's not an excuse to be naked in front of my sister. He told me she was naked too. I told him it doesn't matter.