Forgot the Tab

I spilled water on my notebook at work tonight and messed up a customer's order. I couldn't face them after that, so I just pretended everything was okay when they came to pay. I told them their order was already paid for by someone else. They were so nice about it and left without checking the receipt. Now every time someone walks in or leaves, my heart drops, wondering if they're coming back to ask about the bill. It's such a tiny thing, but it feels like a big lie hanging over me.