S-O, I'd say that two weeks is sufficient time for you to inquire about your status without seeming like a pest. Call or email the recruiting service and ask if they need any additional information from you.
Generally, screening forms are collected before a formal interview, so in your case you'd just be waiting on the hiring manager to make a decision. Brace yourself as well, since there's a chance that they already filled the slot with another candidate and failed to let you know. (This happens OFTEN with LM--remember that it's a very big company, and communications are somewhat challenging.)
Remember that even if you were passed over for a better-qualified candidate, the use of a third-party recruiting company is a sign that the company needs MANY qualified applicants, whether it's due to them standing up a new program, or because of high turnover. In either case, be sure to mention that you're still available for any future openings in case another candidate drops out. It's pretty common for new hires to be denied security clearances, or for entry-level positions, a candidate might find a higher-paying job and decline LM's offer. Either way, this position could mean that there's opportunity for advancement.