Okay wow! I just learned a TON on how fly works and what was happening behind the scenes when you run attach.
I thought I would share with the community my experience:
I had NO IDEA that attach was creating new databases and setting the app’s connection string to that database, this was 100% my issue prior to needing the ?schema=public.
First, I created my fly postgres app, connected my first app with attach and then started using the app, creating things, etc.
Next, I created the next app that is suppose to share that same database, but I was not seeing the data, I assumed there was some issues with the schema and possibly data being created elsewhere, (I was definitely confused lol)
Now it all makes sense, the second attach command was creating a new user, password, privileges, AND a new database.
I guess I naturally gravitated towards attach early on thinking this was doing some internal *“magic” * to allow networking, etc.
As it pertains to the original post, I was able to login thanks to @shaun 's suggestion above (as I actually never saved the password from the second time around when I recreated the database).
running: psql \du and psql \l was eye opening and I immediately understood how it was all working!
I wonder if attach / detach is the correct terminology? I would also be tempted to think that if this is the correct terminology, that it might be pretty common to have multiple apps connected to the same postgres server and the same database.
After digging a little deeper into the attach api - I can now see that there is a argument for --database-name 
.
Again, just wanted to share my overall experience with postgres and multiple apps “attaching”, etc.
Hope this helps!