B.C.
Sounds like you got it all cleaned up.
Consider it to be over.
Don't worry about it.
Additional:
Just because it's brown doesn't mean it's poo.
Poo certainly would stink even if it were just a trace - I think you would have noticed it a WHOLE lot sooner.
Other possibilities are melted chocolate, mud, melted brown crayon, pudding, cookie, chocolate ice cream (if someone dropped it, he could've stepped in it), etc.
You might not know what it is but it really might not be poo at all.