I thought maybe the plumber guy was there to investigate the suicide womans family, but , did you see the map taped inside his cabinet? It looked to be the whole street mapped out with family names and Terri's character had her picture and said "Something ASAP" could you tell what it said?
That was definitly a childs toybox, but I can't believe it would be a dead child, even the son knows about it, and this show is kinda a comedy isn't it? It could be anything, a sexually explicit sculpture that they didn't want anyone to see, so bury it, remember the letter said "I know what you did, I think its sickening."
I have got to tape this show so I can run it again to get things that I miss, the show Lost is like that, too. Seems like there are things that can be clues.