I've lost many a great item to lava, to creepers, to the void.
Had to be the most embarrassing one, I was disposing of enderpearls on a realm map, and hurled my fully enchanted mending sword into the void along with the pearls.
Mining obsidian to make another ender chest got blown backwards into lava by a creeper.
Making my nether tunnel from spawn to my base, wasn't paying attention to the fact that the floor disappeared, walked off into a lava ocean. Six separate times. :/
That's why we play with keep inventory now. Because I'm dumb and whine a lot when I lose my good gear. xD