@smith6969trains eBay Standard Envelope (ESE) is a metered letter mail shipment with USPS so it does not receive traditional tracking scans like a package would, and the clerk at the PO counter cannot scan it or track it. The envelope is scanned by sorting machinery at distribution centers along the way.
If the envelope is too rigid or thick it won't meet USPS machinable letter requirements and won't receive scans.
With ESE, a 'delivered' scan generally occurs when the envelope arrives at the last USPS facility before it gets to the buyer; sometimes the buyer will receive their order a few days after the delivered scan. If the item was just scanned as delivered, I suggest waiting a couple more days for the envelope to turn up.
If you prefer traditional packages with tracking and are willing to pay for it, you are welcome to ask sellers before purchase if they will add that service to the listing. The rate for that service ranges approx $5-8 for an up to 4 oz package. The seller also has to physically pack the item differently so they may add on a cost for packing materials like a bubble mailer, etc.
Sound expensive for those under $20 items? Then deal with the economical letter mail service and potential lack of tracking updates. You still have buyer protections if those items are never delivered, same as any other tracked service.
