I have the same exact thing happening. I deleted the app a few days ago when was surprised to see it in my app list.

I had previously downloaded the app but and removed it because I never used it. A few days ago I noticed the app when browsing through my app list and thought maybe I didnt delete it properly, so I made sure to delete it. Then this morning my iPhone updated software versions and I found he Headpsace app again on my home, except this time it was grayed out and waiting for me to go on wifi to download.

I just deleted it again but am equally dumbfounded

That's interesting that it still showed up on your homescreen despite not being able to download