How do I obtain my audit number for my Texas ID if I don't have a copy of my ID anymore?

I don’t think you can, because the audit number is a unique number. It changes each time you get a Drivers License / ID. If you lost it I think you have to go DMV.

Do you have your ID number?

Go to the DMV. Be sure to carry your Social Security card and a copy of your birth certificate with you. You might also need to take a recent utility bill with you to prove that you live at the address of record. They can look up your information and issue you a new ID. It’s a pain in the butt by design so you’ll think twice before being careless again

Yeah. It’s called a “real ID”, as if the old ID wasn’t real and this one is. (Somebody in our government had a real brain fart with this one.)

And then if you are unfortunate enough to move to a new state, you’ll have to go through the whole rigmarole again. Because your old Texas ”real ID” isn’t going to be real enough for your new state. Maybe theirs is more real, or something! Go figure. If you fly you’re going to need that “Real ID“. Don’t be real without it!