Final answer:
The item stolen from the sailor that was used to murder the old woman was a spear, as described in Heliodorus' The Ethiopian Story.
Step-by-step explanation:
The narrative provided suggests that the item stolen from the sailor and used to commit murder was a spear. In the excerpt from Heliodorus' The Ethiopian Story, it is described how, in her frenzied state, the old woman accidentally impales herself on a spear that stood up, hence meeting her demise. This spear may have been stolen from the sailor, as it is the weapon involved in the murder of the old woman.