I have a 13-yr-old son. The only parties he has gone to are always parent-supervised. They have all been at rented venues or hotels. There are security guards, no alcohol. They have DJs, dancing. He hasn't been to any house parties.
I don't think you are being over-protective. Kids need boundaries. He hasn't asked to go to a show yet. He likes a band named Daft Punk, I don't know if they tour but I wouldn't allow him to go to anything where there wasn't a parent there as well.
My first concert was Journey, I think I was 13, we were a group of girls and a couple parents.
Concerts are one thing, house parties different. If my son wants to go to a party that isn't supervised by parents I know, well he just won't be allowed to go.
You are doing right mom.
If he's moping and cut you off from contacting the mom, he may have been fibbing about the mom being there. Kids test their boundaries.
When I was 16, my best friend and I had a great plan..I told my mom I was spending the night at my friend's house and my friend said she was spending the night at my house - the idea was that we would hang out all night. Well, we got tired and it got boring and we went home when the buses started running and of course got busted. Our moms had called each other.
It's all about boundaries, you set them and trust me, they want and need them.