I doubt it is getting spamfiltered, Google has an amazing reputation as a non-spam provider.
I put my form in around November so it doesn't get 'lost in the shuffle' over the course of several months waiting. You need to submit in December-ish, and the cuttings go out in April/May. I try and wait till a week before the deadline to submit.
Two things: It is important you fill out the form properly and completely, and when you submit the order, as for a confirmation that they received it somewhere in the body of your email.
Typically when I submit my order, this is all I put in the body of the message: "Thanks for offering this resource and service to the public. Please find my order attached. Can you reply with a confirmation email so I know the order was received? Thanks again."
If I don't hear anything back within a week, I would go into the Sent Items of my email and 'Reply all' to the original message and inquire whether the order was received. I've always gotten a response to the original submission within 3 business days, though, so .... never had to go back and inquire.