Am I to blame for struggling with drive through orders with no training?

I'm talking about taking orders on the head set. We were short staffed today so they called me in early we were super busy my entire shift. It was me, my gm, and another worker. My boss is the only one who knows how to take drive through orders out of the three of us. Well he had to go to the bathroom for several monites and left the headset. People started coming through. I tried to take orders but was completely overwhelmed and asked them to wait. My boss came back a couple minutes later. I've been working here for 2 1/2 months, and they've hardly trained me in drive through at all. They know I can't do it. I never really asked to be trained but they never bothered. Is this my fault?

Am I to blame for struggling with drive through orders with no training?
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