Depends on laws from every country. Some data needs to be stored for sure X years, usually it's 5, but no idea about there. ISP even have all your ip and pings you do 24/7 for years.
But yep, if it's gone it's gone, or hard to do forensics, but if one of the guys have already proof and can tell the exact match, bet and who did it, maybe they can find something. Who knows.