Replace a blown breaker
If I am reading this question right, you couldn't find the main for your panel, so you decided to try to replace the breaker for a dead heating circuit in the live panel.  Lee Ho Fook.  That could have gotten ugly.  

No offense intended and I may be reading the question wrong, but do you realize breakers are not one-time protection devices like fuses?  You can reset a breaker by turning it off then back on if it trips.  You should do this just once and if it trips again, leave it off until the fault that's tripping it is diagnosed and rectified.  Don't reset it over and over hoping it will hold.  

If that doesn't work for you, call in an electrician.  

Replacing a breaker in a live panel is never ideal, a safety conscious electrician will avoid it if at all possible, it might be unavoidable in a some critical facilities, never really ought to happen in residential.  For DIY, just don't do it.  

I reiterate, if you can't figure out how to de-energize something to work on it, DON'T WORK ON IT HOT, call in reinforcements.