Not knowing how Lowe's works, (I'm a HD fan!) is it just possible that your order WAS ready 2 hours after you sent it in. Then after (just a guess here) FOUR hours they thought you were going to be a "no Show" and put the stuff back. I bet loads of people no show or cancel the order and the store misses the memo.

Some stores punish employees if they take their breaks late. Maybe that's why the CSR "just left".

There are MANY things out of yours, or anyone's, control. Trying to do something like this when you are pressed for time is not a good Idea. Maybe next time you should wait until just 2 hours until you need to pick up the items before you place the order.