Ice floats. Even if the most of the ice in the cup has melted, but there was a little bit of it left, the coin will stay on top.
From my personal experience: while we were away on vacation, there was a power outrage for 24_ hours. Coin was on top, but all ice cream and frozen packaged food was ruined. Not sure about big chunks of beef.
a variant is to put an ice cube out of its container and tilted on the rack inside the fridge. If it thaws, it will fail through the rack and not be where you left it when you check for it.
From my personal experience: while we were away on vacation, there was a power outrage for 24_ hours. Coin was on top, but all ice cream and frozen packaged food was ruined. Not sure about big chunks of beef.