Audi Repair: Overheating A-4, audi a 4, diagnostic test

Question
I have a 2002 1.8 turbo Audi, and I overheated today on the highway.  I let it cool down, added coolant, and then filled the rest up with water like the shell mechanic told me to, now it won't even start up.  Could it be oil related, not enough, too old, etc.... Funny timing but, I received a recall on Audi A-4 2002, because of faulty or problematic Coolant sensors yesterday, but it cuts off at 100,000 miles and I have 112,000.  How can I get it started?

Answer
If it overheated badly, you may have done some damage.  I don't think a coolant sensor will cause a no-start problem, but I guess there is always a first.  Can you get a diagnostic test done to find out if there are any fault codes?  That will help in finding out what the no-start problem is.  The ECT is fairly easy to replace, and are a high failure item on Audi's.  Let me know what you find,  Jan