yea, walmart isn't gonna watch hours and hours of video from 15 self checkout registers to find a $100 lego set, that the person MIGHT still have the receipt for and be sued..
But personally, i use the Walmart App. I have all my receipts digitally, especially now that the register gives you the option to receieve it digitally an/or hard copy. I would LOVE Walmart to come after me days later with a warrant saying i stole something, i wouldn't show the receipt until after they accused me of theft.