I want to publicly call out my ex. for not giving me the concert ticket she had bought me as a gift.
I don't get it. She's your ex. Why is she obligated to buy you concert tickets?
Right, that plan is quite stupid. I just want to publicly call out her bad deeds.
If you've broken up with your ex, he has no obligation to do anything for you. Calling them out will make you look petty and bad, so you should refrain from doing so.
I'm going to do it anyway
What's the point. You need to move on. Calling her out on this when the relationship is over will backfire by making you -- not her -- look bad.