1 dragon left?

I tried searching for information but nothing really came up unfortunately. As of beating Skull/Gold dragon, I got hit with 1 dragon left notice, and Kaiser was no where to be found nor did I get Ragnarok from beating the 2 dragons in Kefka's Tower. Me and my wife are 100% sure we cleared all 8 dragons; so we're wondering if the 1 dragon left is referencing Kaiser.

If so, where do we find him? And if not, then could I get a double check on dragon locations to make sure we didn't miss any (that or loaded a save where one of the dragons we beat before was no longer beaten.)

The dragon countdown is not counting Kaiser. As far as dragon locations:

1 in Narshe Fields (where the first Kefka battle is)
1 in Mt. Zozo
1 in Ancient Castle
1 in Opera House
1 in Fanatic's Tower
1 in Phoenix Cave
2 in Kefka's Tower

Interesting. Wife insists we fought all the dragons. Is there a way to confirm this without backtracking (and therefore dealing with all the encounters) such as an item drop/reward list?

Most of the dragons' drops are items you have access to more than 1 of, so not super easily.

I recommend just warping out and checking while keeping a save in the tower to backtrack to.