I think I do not get your point, do you mean that there should be a .hide style in https://github.com/mozilla-b2g/gaia/blob/master/shared/style/confirm.css ? If it helps, please have a look at line 95 of ussd_ui.js in the "Files Changed" tab above to see the new code when showing/hiding the "Sending..." message to the user. For example, when the message is going to be shown, it is displayed (but with opacity 0) and then the opacity animation is executed ;-) When hidden, the animation goes backward. At least, this is how it works now :-)

I may me loosing something about your comment ;-)