What's the shelf life of a chicken nugget?

So this morning, my first graders are reading to themselves and all of a sudden one of my students yells out...

"Hey, how long has this chicken nugget been in my desk?"

So of course, every child immediately runs over to his desk to see what he's talking about. There, on top of his desk he places one very shriveled, rock hard remnant of a former chicken nugget.

Ummmm.... I cannot remember the last time our school served chicken nuggets for lunch. Seriously, it's been three or four weeks.

The student was a little upset with me that I wouldn't let him eat it (gross) and made him throw his petrified chicken nugget in the garbage can. 

(But of course, I fished it out later to snap a photo.)

(actual "crime scene" photo - ha, ha!)