I have the answer...
I'm a U-verse Prem Tech. The drivers come on a CD located in every single RG (Residential Gateway, thats what we call your modem) box. We don't leave the CD behind b/c after doing this for a year, I've only had 1 person have a laptop w/o an ethernet port.
Anyway, 2Wire must be *****s to not even know that they ship the CD (and mount screws, etc) with their modems. As for AT&T, who ever you call isn't going to know about that stuff. Why? B/C they are some rep in an office and has most likely never seen the modem, an installation, etc.
So, call into Tier 1 tech support if you still have this situation and demand that a "prem tech" be dispatched to give you the CD.
Good luck!