I Had Several Columbines And Coreopsis Plants Disappear. What Would Cause That?

Question

The plants weren’t dead they were gone. It happened over the winter. Other plants in the area were fine.

Answer 1

They should die back for the winter and return in the spring. If they didn't it could be for a multitude of reasons. They could have been annual instead of perennial, deer or other critter could have eaten them, the freezing and thawing of the soil could have heaved the roots up, killing them. It also helps to mulch well for winter protection.

https://www.gardeningknowhow.com/plant-problems/pests/deer/deer-resistant-plants.htm
https://www.gardeningknowhow.com/ornamental/flowers/coreopsis/coreopsis-overwintering.htm
https://www.gardeningknowhow.com/ornamental/flowers/columbine/columbine-flower.htm