I just had a similar thing happen but with a much smaller (under 2kg item).

Hadn't arrived by the last estimated delivery date so looked up the tracking number. Parcel had gone with toll priority rather than been posted. Toll priority do not deliver to my town. Came up in the tracking as a successful delivery several days earlier in the closest major town which is a 320km round trip away. I messaged the seller to ask them to check for me. They said not their issue and call the courier.

Called the courier they said it's at the depot and won't be delivered as they don't service my area. I needed the item urgently so I went to grab it the next day. Courier depot in town tells me it's not there any more as it was onforwarded with Australia post. Could've told me that before I came to get it..... We only get our mail twice weekly so had to wait another 3 days for it to come in the mail.

I'm annoyed the seller would courier such a small item rather than post it. The listing said they use post for small stuff and courier for other stuff. I know it's not really the sellers fault but it's hard to be happy with a purchase when the cost for fuel to collect it outweighed the item cost.