Reversing a reversal!

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Hi folks. So, I'm feeling a bit dumb. By mistake I have deleted a Sales Invoice (which has been paid and reconciled) and Sage is telling me it's marked as 'Reversed'. My first thought was to recreate the SI so before I did that I checked to see if the customer's payment was now recorded as an unallocated payment on account. It isn't. My bank still reconciles. If I create a replacement SI then surely I'm creating an outstanding transaction? This is presumably very simple but I've gone down the rabbithole and I'm confused. Anyone offer me some advice?