Here is a small video of me checking a breaker for water damage.
As jumpers pdf reads all romex that got wet then it dried, should be replaced. Opinions vary, but thats from the manufacturer.
It's obvious any connections that got wet will corroad.
If any water gets in the panel too, it can definetly cause corrosion. And we all know corosion and electrical parts don't work well together.
In the old days I tried to trip a breaker by putting the hot on the ground. One time the breaker would not trip. I went out side to the panel and the wire I was trying to trip had melted all the way back.
I found the 2" opening on the top of the panel had been left uncovered for years.
I broke open a breaker and it was full of a big glob of rust. I couldn't hardly see the spring.
http://www.youtube.com/watch?v=cVz0HAcwNl4