I went fishing yesterday and I retied a uni knot to a new cavitron buzz bait. I caught three good fish and when I went to cast, my cavitron was GONE.  

I checked the line for a break but i soon discovered that my line just gave out. :'(

I figured maybe the knot but I am just wondering, is there a better knot than the uni knot because this has mutiple times over the years. :-?

Palomar.  

http://www.stripersurf.com/knot_terminal.html

Here are some more, knock yourself out.  

http://www.animatedknots.com/indexfishing.php?LogoImage=LogoGrog.jpg&Website=www.animatedknots.com

What brand and line size were you using? Have you checked your rod guides for possible damage? How old is your line?

I use the uni-knot for 90% of my connections with all line types without a problem.

Palomar is the best fishing knot ever!

The Palomar is all I ever tie when I'm bass fishing.

From what I have read, the Jansik Special is supposed to have the highest knot strength though (I usually only ever use this knot when I'm musky fishing). I've never had a problem with this knot either, just takes a little longer to tie.  

How often do you re-tie? After you catch a few fish you should check your line, and re-tie. I'm talking from experience.

Falcon

I have had baits fly into the wild blue yonder, too.

The knot can become weak or get dinged so now I check my knots after each fish or after five to ten minutes of fishing.

I use a Palamor knot. You will use a lot of line when tieing on a buzzbait and you have to watch for line burn when pulling the knot tight.

I also have learned to leave a long "tag" end on the knot (1/4 inch +) just in case it slips.

Once last item...I have had the bait fly away when the line was cut as I was working out a backlash.  I had no idea that I had cut the line on the spool. So check your line after you clear a backlash.

Now, I carry extra baitcasters so I can change out one for another if I get a serious backlash.