Yes they "Might Not" stamp your passport if you use the bus but if they scan you CIE card it will automatically register in the database of Police Federal that you exited the country and left for Argentina!!! The exit stamp in your passport doesn't mean much any more as everything is computerised and will clearly show in thier Database!!!
If they "Don't Scan" however when your crossing by bus then you are in the clear and they won't know if you left! However if your trying to leave Argentina for another country they "WILL" scan your CIE at the airport to make sure it's valid and register your flight out of Argentina which again will reflect in Police Federal here in Brasil's Database!!!
So if you lie on the naturalization application "WHICH IS PUNISHABLE BY LAW" they will know!!! Plus your application might be refused based on those grounds so if I was you I'll consider these two things!!!
1) It's fine if your going to Argentina by bus but if you plan on staying there "MAKE SURE" Immigration or Border Control does not "SCAN" your CIE!!! MAKE SURE YOU PAY ATTENTION!!! If they scan it it will directly register and Police Federal will know!!! If they just look at it and give it back your okay BUT make sure upon return to Brazil they don't "SCAN" it upon re-entry into this country!!! Also make sure if you are ever stopped by the regular police for "ANY REASON" they just look at it and "DON'T SCAN" the barcode, If your CIE is never "SCANNED" your whole trip there It will be like you never left so you will be okay!
2) If your planning on exiting Argentina to another country by PLANE just forget about it because the Argentinian Immigration will want to know how you first got into the country which is by bus, which is fine but they will also want to know if you are legally in the country and the only way to prove this is by handing in you CIE which again is fine, Only thing is as soon as you hand it in they will "SCAN" the Barcode for authenticity and register your flight out which "WILL IMMEDIATELY" reflect in Police Federal's database of where you are and you flight out of that country!!!
The one year of permanent residency does not necessarily mean you cannot leave Brazil!!! You can leave but just leave for important reasons you can "JUSTIFY" such as maybe a death of a loved one or family member (If you can show an authenticated copy of a death certificate you should be okay) you can also use a short term study course abroad as an excuse (If you can show an certified certificate of completion of the course)
The rules or applying for naturalization are clear!!! It does not say anywhere you cannot leave!!! You just need to "BE ABLE TO JUSITIFY" the reason you left as important and your okay. Trying to sneak around is fine if your adventurous just make sure that your CIE is never "SCANNED" anytime from the start to the end of your trip!
How do I know all of this? I have a U.S "Passport Card" the Brazilian CIE uses the same technology, I don't get stamped out when am leaving the USA to a country that accepts the Passport Card Yet all my departures and entry's into "ANY COUNTRY" I present my Passport Card is recorded unto the U.S Immigration database, went to from Miami to England, took a train from England to France to tour Paris with a girlfriend came back to England for my return flight back to Miami, got Miami and lady at immigration said "Oh that nice!!! I always wanted to visit Paris"
How did she know i went to Paris when my tickets were only an in and out flight from Miami? "They Scanned my entry into France" and it registered in the USA immigration database!!!