This is the only time I've had irons come loose.
They have always been rock steady.
I see now, that that can change.
How it did, is a complete and utter mystery to me.
If one hunts long enough, they will see stranger things happen than just sights coming loose. Sights don't come loose or get off by sitting in the gun safe since last season. Scopes don't go bad that way either. The vibrations by the ride to one's hunting spot has probably loosened more irons and jiggle more scopes loose than all other reasons combined. Back in 1968 I bought a M1917 for $25. Stock sight was a peep sight, so I took it to the neighborhood gunsmith, had him cut down and re-crown the barrel and put a set of Williams sights on it. Got it back two weeks before season and sighted it in. Opening morning a nice ten point runs up and looks at me. I looked down the barrel at him and there was no rear sight. Somehow the screws had loosened up and the sight had fallen off on the walk to my stand in the dark. Thank goodness the buck was only 30 yards away and I was familiar with the gun. A good guesstimate and point blank range yielded me a dandy deer. A week later, a new rear sight firmly fastened with locktite and the gun never needed any adjustments for the next 20 years. In the eighties I broke down and put a cheap POS Tasco 3X9 scope on it. Sighted it in and have never had to take the adjustment caps off it again. Lucky maybe? I have a .32 Winchester Special that my grandpa bought after he came home from WWI. He gave it to me the second year I hunted deer. He had sighted it in when he got it in 1919. I've used it and taken deer, and my two sons have used it to take deer. The sights have never been changed since the first adjustment 93 years ago. Even tho grandpa ran over it once after forgetting he left it leaning on the bumper of the truck.
Yes sights loosen up and scopes go bad. One should always check their gun for accuracy before using it to hunt. But not just to check the sights, but to become familiar with it again if it has not been used for a while. I bet unfamiliarity with one's firearm has led to more misses/bad hits than sights/scopes knocked off. Over the years I have seen many situations other than apathy or laziness where a gun didn't get shot by the hunter before season. Sometimes it was a college student home for the first time since the beginning of the school year. They had shot the gun the year before.....but came home the night before season. Seen the same thing with GIs coming home from service or on leave just in time for hunting. I don't begrudge these folks for not shooting and I won't be the one to tell them they shouldn't hunt without shooting their gun first. In all of the cases I saw, they did just fine. I'm not saying it should be the norm, just saying odds are, if one misses or makes a bad hit, odds are it ain't the gun......even tho the gun usually gets the blame. Wish I had a nickle for every time I heard someone blame the scope for a clean miss or a bad hit, but when they sat down and shot at a stationary non-living target, they hit just fine.