The shifter linkage on these machine are the weak point. The shift fork is a spring loaded fork to hold it in gear after it is properly in the correct gear. If it is not all the way in gear it can pop out, so the spring can also work against us. Going thru the puddle had no bearing on your issue, just was not fully into gear when you started out in all probability. I have had this same issue and spoke with the factory service tech who explained all this stuff to me. What I have learned to do as well as many others, is to put it into gear, then slightly tap the gas peddle while wiggling the shifter to be sure it goes fully into gear and the shift fork engages properly. With a little practice it becomes second nature when ever you shift. The long linkage in these has enough play that sometimes it is not fully into the proper shift position, even though you think it is. As far as adjusting your linkage, you need to remove the "C" clip where it attaches to the link on the engine (transmission) and pull the shift linkage off and then the shifter on the transmission can be shifted manually by the arm. The shift lights on your dash are controlled inside the transmission so you will easily see which gear you are into. Move into reverse and adjust the linkage trunion until the hole lines up to the arm pin, then move into low and recheck the hole in linkage to the pin on shift arm. In most cases some happy medium will be needed to get the best alignment from rev to low position, any minor error here is taken up by the spring loaded shift fork inside the transmission. Lock the nut on the trunion, slip the linkage back onto shift arm and replace the C clip. You may want to get a couple spare C clips as these little boogers have a tendency to disappear when you replace them.
Then remember to wiggle your shifter while giving it just a tiny bit of gas to be sure it falls all the way into gear!! Glad your machine performed well for your ride.
