But suppose you call the cops and falsely claim there's a terrorist on the loose in a train station, inciting a stampede of confusion. You should be personally liable for making that false report.
When seconds count, the cops are minutes away.
A more correct analogy would be if you called the police and falsely claime there was a terrorist, and then the cops arrived and precipitated the stampede. Regardless of what the Costco employee may have said on the phone, there was no panic or stampede, nobody got injured or killed until the police showed up and apparently badly mismanaged the situation.