Originally Posted by BIGTIME
ok, sounds like the entire slider with the silver bit has come off. I have highlighted it in red below.
From looking at the vent it looks to be somehow clipped in from the back, so it's able to slide horizontally, but I didn't want to break anything on my spare to figure out how it's clipped in. The important bit here is really if it's just come loose because it wasn't properly clipped in or if some of the plastic tabs has come off. If the plastic tabs are broken, then you maybe need to buy a new vent. Glueing it may be a possibility, but you need to use miniscule amounts to avoid glueing it to the slats.
This is a pic of the other side:
To get the vent off you have to remove the trim. See the "PASSENGERíS SIDE AND MAIN AIR VENT TRIM" section in the link below:
That should give you an idea how to get the vent off.
Steps 2-5 in the following guide should help you take the vent apart to see if it's something you can fix.
Just take your time and don't use too much force!