The item appears under "Cancelled items" (complete with an annotation by me: "Item collected from vendor 11:15 4/12/2021, £40 cash paid, no postage applicable. Vendor needs to advise
eBay that transaction is complete as I am getting spurious payment reminders.").
Nothing listed under "Unpaid items", nor any way to record the item as bought and paid for, other than the above annotation.