Sad news here..Hey I dont know ♥♥♥♥♥ about Dedicated Servers but can they be backed up? by the host /admin.. and yes there should be somewhere logs of whos online etc...
On a seperate thought though ..Clearly though it appears a malicious Party has accessed the server and is achieving their goal of spreading Chaos.. backups, logs access/user rights these are the common tools Online Servers need.. perhaps worthy of logging a ticket to have Ded Server Logs in the future Full release at very least