Say you go with a few friends on a night out, downtown fairly far from where you live. Afterwards, rather than dealing with how to get home, a friend of a friend offers the couch in their shared apartment. Not ideal, but you take it for convenience.
In this case, you wake up at 7am and assume your unexpected host is still sleeping. What's the proper etiquette for leaving? Is it standard to leave an appreciation note before you leave, or wait until the host wakes up?