I am actually in the exact same boat as you
I know that in my case, I recieved the letter automatically because of the online application I submitted, and since I got my first interview and a demo as a result of going into the store personally to talk to the counter manager, I think that the two are unrelated. Hmm.. I hope that makes sense
If you submitted an online application, I would bet that the letter is from that. Dont worry! Hope that helps.