Missing Free Drink on Starbucks App - Need Immediate Help

The Starbucks app could use some enhancements as it can be quite frustrating to use. I misplaced a complimentary beverage voucher. On May 5, 2024, I had 13 stars and purchased two drinks, but unfortunately, I did not receive the complimentary drink that was supposed to come with it. What is the purpose of the reward system if it is ineffective? I feel like I'm just wasting my time trying to earn stars. Why bother including rewards on the app if you have no intention of honoring them? Could you kindly assist me in resolving this matter?