Wow! I've never even looked at my camera's "scene" mode. Little "pictures" in a menu display! "Pet portrait?" "Blossom?" "Child?"
Anyway, not to make too light of the scene mode, FWIW, my thumb rests between the command dial and the LiveVIew switch. I have my D7000 programmed to adjust aperture with the main command dial, since I shoot virtually 100% in aperture-priority mode. I also changed the direction: turning the wheel to the right, opens the aperture to its maximum opening, which somehow makes more ergonomic sense to me than the default direction, which seems "backwards." Anyway, I'm constantly thumbing the wheel subconsciously to the right to "try to let in more light" while shooting (90% of the time, I'm shooting wide-open). What I'm saying is, the wheel is in constant contact with my thumb, and my thumb knows it's there, always adding slight pressure to the right, to ensure my widest aperture is "set." This "presence" (both tactilely and mentally) seems to keep the dial in check. Once in a great while, I may have bumped it inadvertently to an f-stop I wasn't wanting, but it seems, rarely.
If I'm shooting at a stop other than wide-open, then my thumb seems to "know," and seems to instinctively lean more toward the LiveView switch, away from the command dial.
This doesn't address your specific question, but if I could make a suggestion: that you consider weening yourself off of the scene mode, and try shooting in aperture-priority mode for a week (perhaps even setting the command dial to control aperture, if desired), and see how you like it. Other than that, tape always works for these kinds of issues. In my TV job, some people tape a plastic water bottle cap onto switches we're not supposed to change inadvertently.
