Anybody who has cast even a sideways glance at hop plants will know that leaves from the main stalk come in pairs. This means that it is very obvious when some are missing. Imagine my surprise then when I looked up the other day and saw this:
There is also one missing from further up above the level of the deck (yes it has gotten that far up). Here is a close up of where it looks like it has been pulled out of the stalk:
As you can see it had just rained. Can't imagine it rained so hard that leaves were ripped out. It does rain like it means it here in Houston though. I found a leaf on the ground being consumed busily by woodlice and snails:
Maybe this one was just one too many to carry away for whomever or whatever fancied them. Another, slightly more prosaic, answer that was suggested by my other half is that one of our cats had been left out on the balcony and had jumped/clambered down taking several leaves with him. He has a history of jumping from the balcony if he isn't let in quickly enough for his liking. I have to say I still prefer the idea of some urban wildlife Raffles character snatching them in the night. Just hope they got all they came for.