The documentation that you sent the letter to ATF and they stamped it and sent it back would seem to be evidence that you notified them. ATF just doesn't care. Nothing in the MD regs says ATF has to care.
So how's the judge going to rule now since you can't even notify ATF of your possession of a rapid fire device (ie motor oil). No way you can comply with the law as passed by Maryland.
All we had to do is apply by 1 October 2018. I did. Anyone who still hasn't indeed cannot.
The fact that ATF is returning them with a stamp shows that they received the application. A built-in return receipt and date stamp. That is a nice feature that our federal government has decided to provide for a change!
If you sent in an application whether postal mail or e-mail by 1 October, you're in better shape law-wise than someone who did not. (IANAL)