If you coach is like mine, the fuse that serves the 12V "cigar lighter" circuit is number F58 on the Front Distribution Panel (FDP). That's the big circuit board in the compartment (accessible from the outside of the coach) under the driver's left foot. Fuse F58 is in the upper-left corner of the board. It's a 15A ATM fuse.
That fuse is powered off the house switched battery bus. There is a Ford "cigar lighter" circuit as well. On my coach, that circuit is not connected to anything, so checking the Ford fuse for that circuit is unhelpful.
By the way, the owner's manual and label on the FDP cover will call that fuse "AUX 12V PWR (OPT)." It most assuredly is not "optional."
2008 Holiday Rambler Admiral 30PDD (Ford F-53 chassis)
2009 Honda Fit Sport