Snapshot Inventory Clearer

Recently I have just done a video on the recent snapshot review 14w17a and I was reviewing for You Tube. Once I was done with the review I had gone into the latest released version for MINECRAFT and that was 1.7.9. But the only problem the once I had gone back into one of my own single player worlds was that all of my inventory space and blocks and items in chest, (etc) was completely gone. That means that for an example if you had three stacks of iron, that would be all gone. I've noticed that this would appear in the past snapshots as well. I dont know if there can be anything to help out this issue. But all I know is that it gets very annoying trying to esitimate all your items back into the game. So I would very likely to fix this thankyou.