If they didn't immediately set up for an interview during that call then they've moved on. There are people ready to die for that job so they probably took them. Move on. You sound like you're young and inexperienced which is fine, honestly Costco probably wouldn't be a good fit for anyone "looking for something part time". You're basically working 40 hour weeks and will not have any downtime during the job, you're always doing something. Consider that and then reapply toward the end of summer if you're really interested. I quit not too long ago after a couple of years, and if you're not in it for the long-haul then you're going to get burned out within 9 months. Costco helped me to appreciate other part-time jobs a lot more and the experience definitely changed my life as to what I personally seek in a job.