I think I did it. I went through county by county in the texas brand registry, and e-mailed every ranch in every county that I found something similar. I didn't e-mail the ranch she came from, but I DID find someone who knew the guy I was looking for.
I haven't talked to him yet, but he's Larry Holder of Holder Quarter Horses in Knox City, TX. Looking at all the horses pictured on the site, they all have the number in the same spot on the shoulder and the butt, and only one number on the shoulder. There's also at least one horse (beware, they're terrible quality)
Where you can see the wavy things. I'm still not sure what they're called...but it's the only thing I've seen so far that looks identical.
And guess what guys, ALL his horses are registered.
I was also told, if I could just get her registered name (or hopefully her number), I can call the AQHA and ask them for an Application for Duplicate Registry for a lost registration. So I could get her papers. Now. I just have to muster up the courage to call him. I wish he did e-mail, but he seems like the old gruff and tough cowboy who probably doesn't even know how to use a computer lol