Step son had a bad birthday. Does his mom have a right to be mad at me

Today we were having my step son's 15th birthday party. His mom did the party last year so it was me and my husband's turn. When figuring out what we were gonna do I had coupons and discounts for this ropes course I used to take my twin boys to all the time. It would be cheap because of the coupons I had. My step son has a fear if heights but when I brought it up both my sons wanted to go but my step son didn't. I told him this way he can face his fears and to look at how excited his brothers were about going. After a lot of convincing he caved. He invited several people from his lacrosse team. It was me, my husband, step son, my son's, his mom, and 10 other boys and 3 girls. I think he liked one of the girl. He was talking to her a lot but maybe they're just friends. We ate cake and stuff at the house an opened gifts there and then headed to the ropes course. Me and my step son's mom don't get along but we were trying to be good for his party. She kept criticizing the party and saying how he doesn't like heights and this was a dumb idea but I just blocked the bitch out. At the ropes course they had harnesses so my step son would be fine. It has like 15 levels. After about 45 minutes everyone had completed the course but I didn't see my step son. When we found him he was stuck at level 6 and was hugging the giant wooden pole things. His dad yelled if he didn't want to finish to just come down but he was frozen up there. He was having a panic attack and everyone was trying to get him to come down. He had a harness so he was being a bit over dramatic. After like 10 minutes of him refusing to move his mom had to go up there to get him. He still wouldn't move at first but after another 10 minutes of her talking to him she was able to help him down. He was quiet the whole ride home and after all the kids left his mom blamed me for all of this. He got stuck. He didn't die. She's pissed at me when what happened honestly wasn't that big of a deal. He isn't hurt. My step son is upset. We all still had a good time. It may have not been the best party but it wasn't a huge deal.

He wasn't embarrassed he was scared. He has no reason to be embarrassed. He just got a little scared.