Bored bunnies tend to act up, actually. Particularly the younger juvenile buns. IF they are seriously bored they might start to chew on things they're not supposed to, make noise to try to wake you p for attention, kick their poo all over the place...
I know how you feel - I used to work crazy hours at the office, and so did my husband. We left Kirby in the house for 14 hours alone at least and he always kinda just quietly roamed out, took a nap, ate, sat... very regular bunny stuff throughout the day (crepuscular, as Laura mentioned). I had a webcam on him and I looked at him all the time at the office, so I see what he occupied his time with. While I felt he was bored, the truth is he probably was just fine. In fact, over time, I got to know my bunny better and have learned that this particular bunny enjoys quiet, does not like racket or music, or being disturbed too much. He is very happy on his own and so he doesn't complain.
It could just be our human psychological standard for seeking companionship. Bunnies ARE social animals, but single buns very often do just fine with hours of alone time.