Restore to stock without PC connection?

So I'm on the original stock firmware (AOCE), was rooted with PingPong (since 4/2015). Phone stopped doing fast charge so I was going to wipe and go back to stock with ODIN for troubleshooting when I also found that the device will not be recognized by PC either when I went to pull files. Drivers are fine, see's the gf's Note 4. Download mode isn't recognized either by PC or by ODIN. When plugged into PC, just get 'Cable Charging'. So I called AT&T and they're going to send another one out..... So how f'd am I? After factory reset, running the AT&T update fails, so I'm guessing there's still stuff on there in the /system partition or other 'protected' partitions. Without the ability to connect to it, are they going to find the root stuff? (completely hypothetical)