HELP! My Car Lost it's Tune!

Contrary to popular belief, if your car starts, there is definitely a tune file on the control module. The factory engine control module (ECM) cannot 'flash itself back to stock' in most cases. As a general rule of thumb, the ECM will not modify a tune file from what was flashed, there are some adaptives in place to adjust for poor fuel quality, elevation or air quality, and road conditions. As with every rule, there are exceptions; in some late-model vehicles, the additional OnStar module does have this capability. If you are tuning a C7 Corvette ZR1, C8 Corvette, or 19+ Silverado, for example, this is something you prevent from happening by purchasing an unlocked PCM from HP Tuners. These have been modified to eliminate this issue. For non-factory ECMs there are occasions where it will lose the tune and the file needs to simply be reflashed (rewritten) to the controller. 

The symptoms of an ECU not having a tune file are a no-start, condition. If your car is attempting to start i.e. cranking, but not fully turning over or will run, but has some drivability issue, then you have another mechanical or tune issue. The best way to help your tuner address and diagnose this issue is to gather some really specific information. If you are using HP Tuners to tune the vehicle, they will want a datalog of the vehicle while it is performing the less than desirable action. They will most likely prefer that use their specific channel configuration in the VCM Scanner. If COBB is your platform of choice, then creating a log utilizing the handheld provided when the tune was completed and send that off.