No pins with mine either and I can't find them in the parts listing.
Are they just regular 1/8" hairpins?
Last week I installed my mulch kit and put the deck on the tractor. When removing it I also had an issue with the left side latch not wanting to release. A couple of jolts on the pedals to & fro and it finally came free. If the weather holds this weekend I may get under there to make sure everything is adjusted properly.
I did have the deck resting on a 4'x3'x1/2" thick stall mat so maybe that extra 1/2" had something to do with it. Or, maybe it just needs to work in all the connection points...
My dealer did an awesome job with setup and even delivered it to me with a full tank of fuel. However this is the first I've seen or read about those pins on the new style mower deck lift arms. I've never had a problem with the latches coming undone.
If OP has individual left/right latches then he has the new style, like I do. And sometimes, even though my deck normally removes and installs without any problems, sometimes one hook or the other just won't clear the latch. All I've done the couple times this happened is given it some persuasion by running the tractor a few inches forward then a few inches back, basically juat have it in low range and give a quick stab on each travel pedal. It'll unseat eventually.