Yes. A closed car in the sun is an oven. Soy-coconut will slump, sweat, and sometimes come away from the glass. Paraffin holds its shape longer and then goes as well. Fragrance oil beads on the top. The lid may glue itself down with scented soup. None of this means the candle is ruined. It means you left it on the passenger seat in July.
If it already happened
Let it cool level, or you will have a permanent slope. Blot the oil. If the wick has vanished under a slump, wait until it is fully set and dig the wick clear with a cocktail stick. Then burn it at home like a normal candle. Throw might be a bit quieter if a lot of oil sweated out. Still a candle.
Wet-looking tops after heat are sweating. Gaps at the glass are wet spots.
We pack to survive a van, not a dashboard. Collect from us in Ullapool in a bag, not on the parcel shelf under glass.
