I'm actually not 100% that this will work every time every where, but if it doesn't work it's not any kind of problem. I'll just share the way that worked and you can deduce from it whatever you'd like.
Place an online order for in store pickup. After you pay and it says they're getting your order ready, write down your order number on a piece of paper. Go inside to get your order, but tell them at customer service that your phone died so you can't check in or whatever, but you wrote down your order number. They'll tell you they're getting it ready and you wait. Once they have it thank them and go to your car. Fire up your phone and go back to your order on the Lowe's site. It's going to say your order is still incomplete because you can't check in by handing the rep a piece of paper. They won't know how to process it, or they'll forget to, or whatever the case may be they will leave your order open- ended. Click the stuff to cancel the entire order. You'll get refunded for everything that you just picked up. Probably.
Have a great day!