[waltjp]

Originally Posted by TwoBits

I thought that, too, and was looking for the rule reference, but found this instead:

Casebook 8.2.3 Situation: B1 hits a slow roller to F5 and arrives safely but misses first base. F3 catches the ball with his foot off the base and casually steps on first base, although he believes the runner has beaten the throw. RULING: B1 is out. Because a force play is being made on the runner and the result of continuing action, F3 is required to appeal the missed base and does so by stepping on the missed base.

This sounds like an accidental appeal to me.

Another case play -

8.4.2 SITUATION B: With R1 at first, B2 hits a double into right center, sending R1 to third. However, R1 misses second base. F6 is standing on second when he catches the throw from the outfield. He then throws the ball to the pitcher.
RULING: Although R1 missed second, no call will be made by the umpire because F6 did not make an intentional appeal of the missed base.