LEXLVR07

hello guys I have a 1996 lexus ls 400 and I have a question for you guys hopefully someone can help me.. Today I took my ls to a shop to get rotors installed so he put the car on the lift but he told me to leave the ignition on so I found that weird but I was like whatever he knows what he is doin... then he told me to shut the ignition off to not kill the battery so then I shut it off (I DONT KNOW IF THIS IS OF ANY SIGNIFICANCE BUT I AM JUST MENTIONING EXACTLY WHAT HAPPEND) SO THEN HE FINISHED WITH THE ROTORS AND THEN I TOLD HIM to fix a bulb that was out and he changed the bulb the bulb that he used I dont know he just opened his desk and put in any bulb and then the light went out in the dash letting me know that the problem was fixed so then I thought everything was ok and payed him and left the shop. I was driving and everything seemed ok except the rpms were kind of low and it was way below the 1 but still drving fine then I parked the car and when I hit reverse the car shut off I tried to start it and it started right away and I moved the car and then I drove and it was fine but then I had to park and I put it in reverse and again the car shut off.. dash lights on and all but the car shuts off in reverse.. So my question is if he put the wrong bulb in the rear light can that cause this problem or is something else wrong because I have had this car for 3 years and never had a problem like this I do feel that it was definately something that occured at the shop and was his fault. Please let me know because this is really something stressing me out and dont have the money for right now. Thank you in advance.