The answer is you.
If the tribe have no names, the only way they could refer to each other is direct communication: "You have food?", "You make fire", etc.
In this instance, everyone is you and no-one is individually identifiable.
Note that in this instance, it would be impossible for a member of the tribe to talk about someone else in the third person. That might limit their communication somewhat, but it gets you out of your whodunnit conundrum.