Deleted invoices cannot be recovered directly in Dimensions, but searching for the transaction is worth trying first.
Click Debtors > Customers (ribbon menu) or Creditors > Suppliers (ribbon menu), or use the classic/module menu equivalents.
Click Find and enter the account code.
Click Transactions, then click List Definition.
In the Filter, confirm that both Posted and Batched are ticked.
If the invoice number is known, scroll down in the Search fields and enter it in the Header Ref field.
Set the View to All Years All Periods.
Click Display.
If the invoice does not appear (also check that the number of results is not restricted), it is no longer in Dimensions. It must be re-keyed or retrieved by restoring the database to a point before the deletion.