There are a couple of possibilities. There is a small chance you can blow it back out from the other end with compressed air. That would be easy.
Otherwise, if one rudder line is still through on both ends, disconnect that line on the same side the other line is disconnected. Attach a temporary line to it. Pull the temporary line into the tube until one end comes out the other end.
Then connect both original rudder lines to the temporary line and pull them both through the other way. You can tape the lines over any knot to make a streamlined joint that will pull around the curves. If friction is a problem, use silicone spray if necessary. Make sure first that all lines are anchored on the other end. Reconnect both ends of your rudder lines when done.
If both lines are lost in the tube, you might have to look around for a flexible cable (old automotive speedometer cable or bent-shaft weed whacker cable. Making sure it is long enough and clean except for some silicone spray to lower friction, feed the cable in from one end completely through the housing, tie or tape your rudder lines to the cable and withdraw it with the lines attached.
Let us know how it works.