I've not been griefed but I wasn't sure where else to put it. Every time I log onto the server I revert back to the same position with the same items no matter what I did last time I was on (ender chest is also reverted). I managed to avoid losing or duping any valuable items (I think) but I did lose some items and accidentally dupe some others but I can't remember exactly what
Restarted the server and it seems to be fixed now. Seems like the server wasn't saving player data for whatever reason, but that also means I can't really do anything for you considering the distance you traveled and the items you got.
It's still not fixed for me - I logged on and it was happening again