Michelle James, 45, from Beddau, Rhondda Cynon Taff, made the grisly find after unwrapping layers of plastic, cardboard and tin foil in the shared garden in Trem-Y-Cwm in November.
She discovered the skeleton of John Sabine who was last seen in 1997.
His late wife, Leigh Ann Sabine, is the main suspect.
She died from cancer on 30 October last year, aged 74.
Ms James told BBC News Leigh Ann Sabine had previously told her it was a medical skeleton stored on the patio.
After her neighbour died, Ms James and a friend went to retrieve the "medical skeleton" to play a prank on a friend.
But after cutting open the plastic, Ms James said: "All this sludge came out over my hands and I was screaming, I was shouting 'it's a dead body, it's a dead body'."
She was initially arrested on suspicion of murder, but Ms James was later released without charge.
A woman has told of her horror at discovering the decomposing remains of her neighbour's husband on her patio.