How did that happen?

We went to a rather larger S mkt than our usual, in the hope of having more choice, for some reason, S*****s wont reopen their fresh fish, meat, and Deli counters.
As usual, I pushed the trolley and Redilady filled it. We hadn't even got into the store, I turned to wipe the trolley handle and when I looked back the trolley had bloomed. "Oh, it just fell in as we passed", I was told.