Harris county keeps the cases confidential for 30 days. You would not be able to find it online. The attorney sent you the documents without the case number, because when you efile it, the case number does not issue for several days. It does not sound like the attorney has done anything wrong. Perhaps they promised you documents faster than you are going to receive them, but you cannot go to court until 60 days have passed based on the prove up statute.
You may be able to keep the car provided you can afford the new proposed payments in a chapter 13 bankruptcy. The new payment would be the total principal divided by month 36 to 60 with a interest rate of about 6%. You may be pay the value of the vehicle provided you have owned it for about 2 1/2 years also, which may lower you payment further.