Server completely ruined upon booting up and loggin in

So I booted up my server that I use with friends to screw around and I immediately noticed that something was really wrong. My inventory had been completely cleared. Alongside this, I was completely unable to break blocks, though I was able to interact with certain blocks (crafting table, furnace, etc.). I decided to reload the server to see if that was an easy fix, but to no avail. After trying numerous things, I found out that any items in your inventory upon leaving are completely deleted, and this is true for EVERYONE on the server. You cannot break any blocks, nor can you have anything in your inventory upon leaving. It completely ruined the server that has hard work and effort put into it. Before this occurred, I switched the software to spigot/bukkit to look at some plugins, though I inevitably turned it back to vanilla. Data backups do not work, as items are continuously deleted upon leaving and/or joining, and the block glitch does not solve itself. Any advice is helpful, as I really need to get this server back.