I remember once a Hungarian passport control officer was very confused that she couldn't find my entry stamp when I was flying out. I had remarked to myself that it was odd they hadn't given me one when I arrived, but didn't think of it again until confronted with a non-English-speaking passport control officer who couldn't find the required stamp. After a few minutes of pantomime and shrugs, she stamped my passport and let me go. I'm another white male.

This isn't particularly helpful to the OP, but this is one reason why I always quickly check my passport as I walk away from the immigration counter. Not only have I caught missed stamps but I've also had an officer erroneously use the "exit" stamp when I was actually entering the country.

This is very true as well. It seems to be very common when landing in Madrid, more often than not they don't even open my passport and just hand it back to me.