It is not normal. If you left it on, it should still be on. However, this is not a good idea. You should always shut down your A/C whenever you park the car. Leaving it on allows the compressor to be left under pressure, which, over time, can lower the service life of any and all seals in the A/C system, but especially in the compressor, as well as causing leaks over time. leading to loss of refrigerant.