This was almost a decade ago, but when I was a bagger we would help people unload their groceries into their car fairly often. It wasn't at all weird to ask for help from staff. They have other things to do but other than the cashier it's almost always non-urgent and a lot lower priority than helping out a customer. Then we would just take the cart back when we went back inside. Grabbing a wayward cart along with others isn't much of a hassle either but they can roll into people's cars if they're just left on pavement.