I unfortunately do not have a picture for this story; I hope that my descriptions are enough to paint a suitable picture.
As I was picking up trash around the cookout areas, I saw many curious things.
Among them was proof of a family cookout, or so I presume. There was a burnt foil wrapping tossed to the side, fluttering in the wind; clearly, it had been used to cook something.
Another article of trash I saw was a hi-chew, a candy highly popular with children; I also found multiple (too many to count) Coronoa bottle caps - it seems that Corona is a popular choice for all park-goers that drink.
The final items that sealed the deal were some scattered paper plates and a sticker from a grill, explaining all its features and advantages. It was conceivable that the group that held the cookout had bought a new grill, and after their eating and drinking was done, they left their plates and sticker from the brand new grill for the park to... remember them.
In the end, it is impossible to know exactly what happened since I was not there; however, it was rather amusing to look at the evidence left behind and formulate a plausible story for the trash.