i guess i'm confused and need more info (a pic could help a lot too). how did it come apart? while driving? did the outside race just fall loose over the post? there shouldn't be any pressure from anything on that bearing...it sounds like it may be a defective bearing. contact robin or sam and they should get a replacement out to you.
if they can't help, it's a
5x8x2.5 bearing.
one thing that could've caused a problem is too much loctite that may have dripped into the bearing...which will cause it to seize up. although you're saying it's a bottom bearing, which is less likely...