Glad you got it back in tact
I wouldn't have thought that the old key would still work, as to if the car would start, I really couldn't say. What do Renault say on the subject?
TBH, if I was the thief I would have thrown the key as it would be evidence connecting them to the crime.
But I guess if they were all smart we wouldn't have the please of the dumbest criminals shows on TV