When I have had this, the card has been inserted into the letterbox by the regular postie on his mail delivery rounds. I have had this on multiple occasions when using a courier company that "outsource" the final delivery to Australia Post. Rather than Aus Post pay for their contract parcel delivery driver to deliver the package, they just deliver the "we missed you, please collect from local post office" card.
I have complained to both the original freight company (DHL in my case) and to Aus Post, since I have paid for delivery to my home and have been expected to collect from the post office.
So don't assume that its Startrack's fault. If they use Aus Post for the final delivery, then it may be Aus Post that has failed you (as they did with me) and they may have never actually tried to deliver - just sent the notice with the regular postman. In my area, the Aus post contract delivery driver is great and always comes to the door. I see his van (from my home office window) and meet him at the door, often before he gets to knock. If I am not home, the cards he leaves are blue and the writing scrawled as he is generally in a hurry. The cards left by the regular Aus Post postie when they have not really attempted delivery are red and always very neatly written. I quizzed the Aus Post Contract Parcel Delivery guy and he assured me that he does not have any red cards and those have come directly from the local post office.