It's actually impossible to miss the item in Bevelle - upon approaching the chest, Tidus automatically proceeds to open it.
Go into Baaj temple to ascertain which temples you've yet to complete. Most are pretty simple, though if you're a first-timer [which considering you're asking, you are

] you might run into a brick wall. Use sites such as GameFAQs to help you find the easiest route through the temples if you don't want to bother yourself.
In Baaj temple, the statues represent their individual temple. I'll list them and work in a clockwise direction, starting from the first statue on your left:
Zanarkand
Macalania
Besaid
Bevelle
Djosé
Kilika
You can pretty much tell which is which by the colours though.
For Zanarkand's temple, you have to light up ALL the white squares in both rooms, as opposed to the coloured ones. Touch even one coloured shape and everything will reset, so make sure you figure out which is a square before stepping on the light. When you're done, proceed to take the Destruction Sphere from the first room and place it where the Besaid sphere used to be, in the second room [the right-hand slot]. You'll receive a rod for Yuna.