my manager did this to me also when i quit, but i will say she 100% did not like me so i’m blaming that. If you and your manager have a good relationship, i would ask them about it!

You're entitled to work those shifts whether the SM likes it or not

I learned at an old job (not Starbucks) when someone quit, it was actually policy to get them off the schedule asap despite giving 2 weeks. Reason given was they'd slack off, might be tempted to steal or be rude to customers or coworkers because they were on their way out. Perhaps your boss came from an old job with that kind of thinking? Either that or they saw an opportunity to get used to being without you right away and took it? It's certainly crappy since you built that time into your plans and are expecting that last paycheck. Try to talk to your manager and see if you can get some hours back. You quit the right way so you wouldn't burn any bridges and have a path back (even if its not entirely true, imply it to put them at ease about the "slacker" fear they might be having about your last week).