If you are Cloaked and Ion'ed, you can not Decloak (because you never reveal a dial), right? I seem to have misplaced my Ion card, but I believe no dial-mechanics work with it. Thanks.

Yes.

The " immediately before you reveal your dial" is the trigger for decloaking and is required to be able to decloak. And Advanced sensors won't work if you are ioned either, for the same reason.

The idea of decloaking, cloaking, and decloaking again before revailing your dial is stopped by the once per trigger of "revealing your dial".

You also may find it helpful to grab the most recent FAQ. They've included all of the rules from the supplement cards and such in it, so it can replace the ion rules card.