I understand that things can happen beyond our control, @asabusiness.
I'd like to help and get this sorted out. The option to recover your deleted invoice isn't possible in QuickBooks Self-Employed (QBSE).
As a way around, you can ask for your customer to send you a copy of the invoice you sent to them. Moving forward, you'll want to check the Send me a copy box when sending the invoice. This way, you'll receive a copy of the statement in case the same issue occur.
I'm also adding this article that serves as your guide in preparing and filing your return: Use reports to fill in your tax return.
I'll be here in case you need more help managing your invoices. It's always my pleasure to back you up.