code: public Participant getParticipant(String participantPrivateId) throws OpenViduException {
  		for (Session session : sessions.values()) {
  			if (!session.isClosed()) {
  				if (session.getParticipantByPrivateId(participantPrivateId) != null) {
  					return session.getParticipantByPrivateId(participantPrivateId);
  				}
  			}
  		}
  		throw new OpenViduException(Code.USER_NOT_FOUND_ERROR_CODE,
  				"No participant with private id '" + participantPrivateId + "' was found");
  	}
docs: Returns a participant
  
  @param participantPrivateId private identifier of the participant
  @return {@link Participant}
  @throws OpenViduException in case the participant doesn't exist