It's hard to envision myself doing anything crazy on my last day (not that kind of person), but the way my STL has been, I'm tempted to do this (and I may not save it for a last day either).
It'll be best if it's a Saturday night and she's closing. I'll go in, grab carts, and do my job as normal. Maybe an hour into my shift, she'll call me on the walkie and say "carts are good, focus on reshop, and don't worry about carts until the store closes." This time, I'll actually listen to her. At some point in the evening, we'll run out of carts. I'm sure guests will complain, and ask why we have no carts. I'll simply respond, "why not ask the manager". And if the STL gets on my case about it, I'll just tell her, "but you told me not to get carts until close. And by my watch, we have X amount of hours until we close".
The only kink in this plan is the GSA/GSTL getting to me first or having a cashier grab carts if I'm unavailable.