Jen, I’m so sorry to hear that. I know how frustrating it is when you are looking forward to making a recipe and it doesn’t work.
Please know that I wouldn’t have posted a recipe I hadn’t tested and didn’t think would work. The last thing I want is for this to happen!
You said that you followed the recipe exactly, so it could have been certain things that caused them to flatten or a combination of things. When cookies do flatten it can be that the flour was just scooped with a measuring cup instead of being added to the measuring cup with a spoon and then leveled off with a knife; a different flour other than all-purpose flour could have been used: the baking powder and baking soda may have been expired; the dough could have been over mixed causing gluten to develop; the oven temperature could be off. Could it be that any one of these may have been the cause?