Not sure what the mechanic was trying to accomplish there . Start by checking for engine codes . This will eliminate a lot of things or point straight to your problem . Also listen for the fuel pump does it hum when you turn on the ignition on without turning the motor over . You should hear a humming sound for about 3-5 seconds coming from the rear of the car when you turn the key on without cranking the engine . If you dont hear this then your not pumping fuel and your car wont start. If can hear the pump and you didnt get any codes then pull a plug after cranking the engine for a while, maybe 30 seconds of cranking . Is the plug wet or dry. If its wet your getting fuel this is good if its dry your not getting fuel . If not then we should change the filter first to ensure were not dealing with a plugged fuel filter. Try starting it if theres no joy then move on to checking pressure on the fuel rail . There could be an issue with the fuel regulator . Next check the injectors . if you have access to a stethoscope then check the injectors while the cars being cranked over if there working you should hear a clicking sound from them . If there not then look for an electrical problem in the wiring harness , check the fuses and relays related to the injectors.
If the plugs are wet then the issue is in the ignition and you would most likely get a code . either coil , or crank sensor or possibly cam sensor . Any one can stop you and are difficult to figure out which unless its casting a code . Best piece of advice that you can take from here is get the OBDII codes read otherwise your just going to replace a lot of stuff needlessly . Hope this helps