Volunteer corn from hybrids which had no glyphosate resistance listed does survive glyphosate application at times.  

I was somewhat puzzled just how I could have missed volunteer corn with my burndown on a couple bean fields this year......right up until I thought about it for a minute, at which point it became quite obvious.  Now if I could just find whomever 'spilled' that trait into my volunteer corn so that I can send the my bill for Matador to clean up his/her mess.