public synchronized PacketReceipt getSentPacketWithSequenceNumber(int sequenceNumber) {
		//ignore N/A sequence numbers
		if(sequenceNumber == Packet.SEQUENCE_NUMBER_NOT_APPLICABLE)
			return null;

		//if the sequence number is for a packet in the future then we haven't sent it yet
		int delta = Packet.deltaBetweenSequenceNumbers(sequenceNumber, lastSentPacketSequenceNumber);
		if(delta < 0)
			return null;

		//if the sequence number is too far in the past then we won't have a record of it
		if(delta >= PacketRecorder.NUM_SENT_PACKETS_STORED)
			return null;

		//return the sent packet
		int index = (lastSentPacketSequenceNumber - delta) % PacketRecorder.NUM_SENT_PACKETS_STORED;
		if(index < 0)
			index += PacketRecorder.NUM_SENT_PACKETS_STORED;
		return sentPackets[index];
	}