my ex's gf knows my bf she's investigating for me?

Is this a bad idea? I found out my ex's gf is from the same town my BF is from and they graduated together. She is with my ex so I don't think I need to worry about her coming on to my BF. She told me I'm not his type. My BF has told me he dated only one girl. I'm just asking questions about my BF asking what he was like in high school to match up if he was a dick like he is now. Do you think it can back fire? (Major investigation here) my ex gave me his gfs number to text him.