How to check if Duplicate?

I just had my first rejection and the reasoning was it was a duplicate. But when I placed the marker it didn't show any existing stops at that location. Is there a way to check all Niantic games before making a nomination without having to install and make accounts on more than just PoGo?
Not a huge issue, but I don't want to clog things up with duplicates. And I just don't want to download more stuff on my phone haha.
Comments
When you send a nomination in Pokemon (as long as you're there) you should be able to see surrounding PoI existing in the wayfarer database (Lightship).
If you're trying to do a remote nomination, then you won't see nearby PoI.
Okay, yeah I noticed it only showed me like the three stops closest to me.
Sometimes there are stops that exist in other Niantic games and not Pokémon go look for an exclamation mark in the map.
I submitted my nomination through the Pokemon Go app (which doesn't show the surrounding POI for other games) and it was rejected as duplicate - is there a way I can see all of the POI as a PoGo player? Thanks!
Pogo does show you all the waypoints, even ones not in your game, on the first page of the nomination process. Unfortunately you have to be standing near the thing you want to submit at the time because it only loads the "nearby" waypoints. If you want to submit remotely then your best bet is to check the ingress map https://intel.ingress.com/ which will show you most of the waypoints in the area. You need a basic ingress account but once you have that there are other planning apps and plugins available to you like IITC.
WARNING- never delete your account in any Niantic game tied to your wayfarer email. The system can't understand it and thinks you have been banned.