Hiding My Cup

Whenever I go for early morning walks, I like to take my coffee with me. But by the time I get to the park, the cup is empty and I really don't feel like carrying it. So I hide it behind a fence at the entrance of the park. This system seems to work well for me... Except when I forget to pick it up on the way out. There's been many a time when the cup has spent the night at the park- even as long as a week, before I remember I left it there.