The other comments are totally on point, knowing that^.
Adding that little bit of fuel shouldn’t have caused it to die like that. Something else is wrong.
If it has spark, its timing is right, has fuel pressure, working injectors and air it should do something. It may not run perfectly because of other parameters but he should be able to get it close to starting and get an idea as to what’s wrong.
I can’t imagine a good mechanic not checking basics like that. A car that doesn’t start at all is a lot easier to fix than a car that once in a while does something weird.
Have you used this mechanic before?