I know it was already mentioned and answered, but seeing as this just happened for me to and it's now six months later..
I originally was trying to find a setting to auto merge all "to do lists", "notes", and "reminders" through Bixby and google, into each other as well as auto syncing to my calendar. Which I've yet to figure out because while doing that I went to tap on my Reminder app within the app area and it disappeared on tap! Insane!
So my easy solution to locating it after unsuccessfully finding it within google app or galaxy store was to go to my settings, open settings, top has a search field and typed it in, located it, clicked on it and then clicked the setting/pinwheel in the top right to bring me deeper into the settings, and under
General I checked off
Add Reminder Icon, and wa-lah, she back.. in all her barely used glory. I now feel complete
. Now back to figuring out my og problem haha.
Thanks yall! 6 months in your future -J