So I took a small break and I'm getting back into my Platinum run. I'm in Trophy Garden, and after around 50 random encounters for Eevee I searched up to see if the thing was even in the garden. Turns out some guy in the area can make a pokemon appear in the trophy garden that's usually not there, and Eevee is among those pokemon. Thing is, only one pokemon appears daily when you ask the guy. One. I'm contemplating either skipping this and just keep the team slot for my HM slave or changing days repetitively. Sadly, changing days screws up some of my other games, including Ultra Sun...
Edit: Upon further research you must have the national dex to get it. Goodbye, Moonlight; and hello, UNLOVED(the bibarel I recently caught as an HM slave)