I was successful on the Mac, but a couple days ago I had been trying with the app too. It works in much the same way (the cart saves, etc.). If you view the cart, click the individual item, and click the "Cart" back button, it will refresh the cart and show the pick up option if it's available. The only thing I was less trusting of is if it was caching my inventory search results.
Thanks! In your opinion is it safer to go the computer route or iPhone?