It depends. If the police suspect the owner has evidence of some sort on the phone, destroying it can lead to a tampering with evidence charge from the police.

A tampering charge doesn't have to be from a court order. If someone eats or dumps out drugs where the police can't collect the physical drug, it will stick.

But in the story's case, it falls within the 100 miles of the US boarder (called a boarder search exception) a warrant, probable cause, or RAS aren't needed here. It's considered a reasonable search so the 4th amendment is limited here.

There is a lot to it and really don't think this is the best format for it here.