How Do You Know That Your Valdo's Map Has Been Added?

Does GGG send a message stating that it is added, or do you just have to see it on the trade site?

I did get my first submission returned to me as I had a cool idea of a Harbinger themed beach map (foil Infused Beachhead) with lots of currency dropping.

So maybe that means my map has been moved to a later date?

Click on your username/profile on the top of the screen next to your 11,
Goto "My Designs", scroll to the bottom, read whats next to Status.

Most likely you can redesign and fix what they complained about.