Tax return sent back with cryptic scribblings - huh?!

I sent my tax return in just before the June 15th deadline (very straightforward - filed forms 1040 and 2555-EZ), and have been eagerly awaiting my stimulus payment.

Well, I just came home to find it's been sent back to me with cryptic red scribblings and stamps all over it, but nothing else. The stamps say "Corr C&E" and "C&E 184", and my address on the 1040 is underlined in red with an arrow pointing down and a big "N" and a small "$" next to it.
 
There is also a stamp showing the postmarked date and the received date.

I'm confused. I've never filed non-electronically before, so is this just something I've missed before? There's nothing else in the envelope except my 2007 return, so I've no idea what all of that means.

  Any ideas?

These are standard IRS input clerk notes. However they usually include a notice saying you forgot to sign or date (or attach a particular form)..did you??

Perhaps you tried to file before you met the physical presence test?

oh dear lord, I forgot to date the freaking thing!! I had some help from a lady at the consulate, and then wasn't sure when I was going to be able to get to a photocopier to make a copy, so I left the date off until I posted it. I guess I forgot! 

There isn't a notice, so can I just date it (with today's date?) and post it off again with a cover letter? Or do I need to send in a new form? And do you know if it will still be considered sent on time?

pah, what a moron! 

oh dear lord, I forgot to date the freaking thing!! I had some help from a lady at the consulate, and then wasn't sure when I was going to be able to get to a photocopier to make a copy, so I left the date off until I posted it. I guess I forgot! 

There isn't a notice, so can I just date it (with today's date?) and post it off again with a cover letter? Or do I need to send in a new form? And do you know if it will still be considered sent on time?

pah, what a moron! 
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don't see any response, so

Ask at IRS.gov about what to do.   Esp. now that tax season is long over, you should get a response back.  Plus, whatever the response is, you can print it out and send it along as part of your cover letter, to show you are doing just what you were told.   
 
next year, just sign/date it as soon as you are done with it.  There's no reason to wait until you are standing at the copier, or in the line at the post office.  No requirement that the date of your signature and date of your payment check (if any) match up.