We don't know if we are silly for not knowing this but neither Wicker or Wilde even thought of this - If you ever leave hand sanitizer in your car and find it FROZEN the next morning . . . throw it away.
And it's not because cold weather ruins it. It's because if it freezes at all, it was probably no good in the first place.
Most hand sanitizers are alcohol-based. So they shouldn't freeze until the temperature gets REALLY low. Like negative-50 degrees or lower.
So if it does freeze, it means there wasn't enough alcohol in there to be effective. Or it was a cheap knock-off that didn't have the ingredients listed on the label.
But almost all the brands you see at stores contain alcohol. So if yours freezes, check the label. And if it's alcohol-based, throw it out.