Call the IRS; they can tell you if the return has been received/logged in, but there is a lag time between receipt and entry into the system. Last year I could track via Airsure as far as Houston (I think). After that, it disappeared off the radar, so I assume it was in the packs on the back of a mule. But it did get to where it was supposed to go.
This year I never got a final delivery receipt, but as it arrived in Austin, I felt pretty secure. I had a refund, and that went into my US account pretty quickly. Refund obviously = return accepted & processed.
Last year I also panicked and was about to send a 'duplicate' via FedEx. I spoke to the IRS who said "DON'T" - apparently it can mightily confuse the system.
As far as FBAR goes, e-filing was simple and instant gratification as I've said before. And from no on, it's the only option.