The most likely cause of the death would be the planting technique or the aftercare of the shrub and not the hardiness. Although if you planted a tender shrub like tropical hibiscus and then there was a freeze (check your zone and your last average frost date) it will die. Do a little searching on the internet about preparing the planting hole and soil, removing the shrub from the pot and handling, watering and mulching practices. Sorry for your bad luck.

Actually we planted several of the same shrubs in the same bed and planted and watered them the same way. The ones in front of the hardy plank siding have lived but the ones in front of the brick section are the ones that have died. Could that have had anything to do with it?