Thats why it tested fine. There were no measurable levels to read as the tank was not cycled.
I dont roll my eyes at you for being new to the hobby, I roll my eyes at the fish store for telling you everything was fine, knowing that yourtank was less than a week old. I had the same problem the first time I set up a freshwater tank and didnt know any better. At least I knew enough to let them test my water....it tested fine of course. About a week after I added fish it sure didnt. Silly lfs
'. It looks like your on the right track now...just get that tank cycled without fish if you can. Good luck!