yearly service

I've used since i bought my car (used). All service has been done there. This last service (not even a week ago) was the standard yearly service. The check over the whole car. It was raining this morning and my automatic wipers kicked on after i pulled out of the garage. The driver side blade was missing and the arm scratched the windshield. I called and asked if they check wipers they said yes. I explained what happened. Service Manger or someone got on the phone and said they don’t touch the blades... well how do you inspect them? They offered no help, no explination and nothing to remediate the 1200 replacement windshield. Horrible service.