Minecraft was glitching, blocks I mined kept re-appearing, eventually, they would be mined. Then I mined the redstone with an iron pickaxe, but it didn't drop any redstone dust to pick up, after I mined 12 blocks, I gave up. I saved. I closed Minecraft and I rebooted my computer. 

When I launched Minecraft IT SPAWNED ME IN A WALL. I died instantly, and I lost EVERYTHING including 8 diamonds, about 20ish gold ore blocks, hundreds of blocks of cobblestone, and other ores. My inventory was full from the hours of mining I had done the day prior. Not to mention, when I re-spawned (after dying), I went back down to my tunnel and nothing I had mined during the glitching had been mined at all, and worse yet, my items were nowhere to be found.