nope that's not water!!

So I am in the Stake Primary Presidency, and our stake is having ward conferences right now. This morning we did the 10th ward in our building and had our ward in the afternoon. I was in charge of teaching Sharing time since we allow all the teachers and presidency to attend the adult meeting the 3rd hour. The 10th ward part went well considering I have NEVER taught sharing time before :) I figured since I was coming back in a couple hours to do my ward, I would just leave my chalk and eraser and other supplies in the room.
When I went in to prepare for my second sharing time, I couldn't find the chalk and eraser. I looked down and they were laying on a little kid chair that had been moved in front of the chalk board. ( a lovely toddler picture was on the board too) When I picked them up, I noticed both the eraser and piece of chalk were soaking wet! I picked up the bag that the rest of the chalk was in and it too was all wet! My first reaction was to look for a cup of spilled water but saw none. Then i noticed a small pool of yellow liquid on the kid chair! EWWWW! I was holding an eraser and chalk and bag that had been peed on! Don't ask my why, I blame this next part on Grant because he always smells things that gross him out, but I lifted the bag and smelled it just to make sure that it was urine!! YEP! it was pee!!!!
Now this is what I don't get...... how in a matter of two hours, did some random kid ( i am assuming was not being supervised by mom and dad) go into the primary room, decided they need to go to the bathroom, and think " hey it would be fun to pee on the chalk and eraser!! Another sister returned the peed on chalk and got me a nice clean sanitary set! I just hope this isn't a sign of what is to follow the next 6 weeks as I attend the other ward conferences!