I ain't perfect, but I have a routine that works pretty good for me. All has gone well for me up until this last trip out to Yosemite. We were out on a three week trip that included going all the way up to WA state from so Cal. Again all went well until our last leg home. Leaving Yosemite, cramped campground to say the least, anyway just as I started hooking up sure enough. Someone needs to get out and my TV is hanging out in the road to get out. Poor guy waited patiently and I'm scrambling to get connected, slides in and EVERYTHING. He finally backed up and found another way out, I finally do my walk around and everything appears to be in order. Start out on our way out of the valley, a good way out and we hear something banging around on the ground. Not sure quite what it was, I pull over and check everything out once again. All appears to be in order. We drive 300 miles to our last "layover" for the night before we get home and after we get backed into the space, I go to un-hitch and behold, my wrench for the over-arm latches (Hensley hitch) for my hitch is gone. Of course it didn't take long to figure out what that banging on the ground we heard earlier was.
As diligent as one may try to be, and it may only happen once. There may always be something to through you off of your game one time. Thankfully, mine was minor and not costly.