The purchase was not actually completed, or was cancelled or subject to a dispute.
The item was purchased more than sixty days ago and no longer appears in the default view.
The item was purchased longer ago than 2021 and is no longer accessible on eBay.
The item was purchased as a guest (while not signed in) or using another account.
The item has been removed by eBay because of a listing violation.
The item has been removed because the seller has been removed.
Try searching your purchase history by title keyword; in some cases that can find transactions that may not otherwise appear in an entire year's worth of purchases.
