Told a lie, filled with shame and self-loathing

A vendor sent us the wrong signs for a conference. We are a technology company and the signs were for an olive oil company. My boss is very angry at me and the design firm I hired to get the signs. My boss leaves for the conference late tomorrow. When I called the design firm, I told them a lie and that my boss was already at the conference with the wrong signs and I needed the correct signs to be reproduced and sent to me overnight. It’s an “emergency” but I lied to make it more urgent. In following up with them, I slipped and said if the olive oil company wants them sent back to them from our office we can do that. The fellow asked me, “I thought they were at the conference.” Rather than admit, that I was wrong and lied… I doubled down on my original lie. I stammered and sounded like and idiot and I’m sure they know I lied. When I hung up, I was filled with shame at my lack of truthfulness and my lack of professionalism. If someone had done that to me, I’d be extremely frustrated. Now I keep getting waves of shame, self-loathing and negative thoughts about my ability to do a good job or even be a decent human being. Big overreaction… but I don’t know how to think about something I did that was clearly wrong. I can’t reframe it. How do you own something that you’ve done that’s wrong and against the person you believe you are? It’s a thought but it’s also a circumstance. It’s a mess. Help!