Removing the knockout plug.?

My buddy installed a garbage disposal for me, and he forgot to punch out the knockout plug. I punched it out while still installed, and now I can not get it out. Is there a way to get it out without taking the whole thing off? I even put my shop vac down there to try to suck it out...No luck. The disposal sounds terrible. As you can probably tell, I am not handy, so try to keep it simple. Please help. Thanks