I only mentioned "slip-by" for the situation where the check-in clerk forgets to ask for the reciprocity fee printout, period. Nothing to do with any special birth or other situations. It has happened (with Aerolineas, BA, Air France, all from Europe), but all cases I heard the passengers had the printout with them on landing anyway.

I have no idea what they do if someone lands without a printout when they should have one. I expect that they must have some payment options in this situation, but I would only be guessing. It is not covered in this otherwise wide and helpful webpage:

http://embassyofargentina.us/embassy...rocityfee.html