I’ve done this at Costco myself a number of times.
“Ah, I just need a bag of coffee and a thing of multivitamins. … Oh, we could use some smoked salmon. And, another bottle of Malbec. Maybe some frozen waffles… Ooh, they’re selling Amish-built sheds!”
And, then, I’m either manhandling half the store to the register, or I’m putting the stuff aside somewhere—looking a bit like one of those careless people who can’t be bothered to put stuff back—and making the walk of shame to get a cart.
I've unfortunately made this mistake at Costco of all places. (startrek.website)