Refrigerator ice maker
" thawed out on its own" HAH! By merely posting your question, you caused the vast cosmic, invisible, forces of the entire DIYchatroom to focus on your icemaker.
" people not closing the freezer all the way." Open door could cause a melting at some point that then refroze in wrong place, like that funnel, that blocked flow. Humidity in outside air could freeze and slowly build up.
If, however you are claiming leaving door ajar caused blockage to melt, I remind you of our powers. Don't mess with our mojo buddy.
Might want to keep an eye on defrost cycle, see that it is keeping build up from forming. If problem recurs try hair dryer in area for kwik fix, then search for cause of blockage or spillage.
Measure twice, cut once.
Look at the nail, not the hammer. Watch the fence, not the blade.
If you hook your thumb over your belt you won't hit it with the hammer or leave it layin on the saw table.