Best case scenario it would rehydrate and be fine, sure enough it is almost completely round again. It also bloomed twice already this year, and is working on another one. Although Costa Farms doesn't label their plants sent to HD, at least Matucana madisoniorum is an easily recognizable species. One feature is it's unusually textured epidermis. It's rough, but kind of like short hard fuzz. It may have spines, be totally spineless, or a bit of both. It's ribs also make it look a lot like Lophophora species, especially the spineless ones.
|Side view, you can see the rib shape and occasional spineless areole.|
|Close up of the flower|
|Rear view, you can also see where it was still sunken in on one side from dehydration.|
I can grow this one in full sun here, it gets shade only for about 2 hours a day, tops, as the sun moves around a large tree in the back yard. I haven't repotted it yet as I usually do with all new purchases. It hasn't fully recovered so I'm taking the risk of leaving it be until next spring. I won't be watering it at all in a few months so it won't matter what it's potted in over the winter.
|Finally starting to look fully hydrated and round again|