Let me guess; your cart was hauled away by an employee who was instructed to replace all carts and all items found in said cart that was left alone for more than two minutes?

Happened to my mom, she was bending down to get bread from a bottom shelf and an elderly person confused her cart with Mom’s cart. Mom is elderly too - But as she told the manager “I’m not stupid.” Her purse was in that cart. She got the purse and cart back.

This is why you should always take your cart with you. Too many times I've wound up picking up more than I meant to and realized I needed a cart... I'd find an empty one, or one with maybe two random tiny items in it, abandoned in the middle of the aisle with no one around, so I'd, of course, assume that it was just another empty cart someone was too lazy to put back. So I'd load my stuff in the cart and then, every time, someone from 50 feet away would come back and be all, "That's my cart." Take your damn cart with you! It's not hard! If you're going to be 50 feet away from it, and it's empty, or damn near empty, with a tiny item that would fit in a basket rather than a cart, you should expect someone to think it's available.