Rereading what I said..... If he has a new account, might be he has no library to fall back on. If so, then he probably did indeed have to start over from scratch. Boy that's a whole lot $$$$$ down the drain pending on how much DLC he had. But I would still think if he's in good standing with Steam/DTG, there should still be some way for him to transfer his games and DLC form the old account to his new one.
If not, here's the lesson I'll offer up to EVERYONE: BACKUP your stuff!!! Not just for you sim, but your entire computer. Put it on a external drive like I do. That why if you lose accounts, delete something you shouldn't have, or your computer decides it's time to go to computer heaven (or hell if it gave who a lot of grief) you're covered. Worst case might be if your computer went bye-bye, pending on what caused it might also fry your external drives if they are plugged in. So another piece of advice. If you can afford it get more than one external drive and keep one with your stuff that's not connected to your computer. I have a total of 4 external drives. Two with a huge amount of tegabytes, one with 12 GB and one with 4 GB.