While I completely understand why you would take they're comment the wrong way, it would have been best to stay calm rather then say "I was gonna do this, but nvm".

Also, did you tell them you had sent the picture? That's something you should definatly notify people about. Here, post generally takes two weeks no matter what I seem to buy, so once it's been a few days to a week after that, I'll let the artist know to see if anything might be up.