If you don't fall for ebay's bait, then you won't lose out. While there are plenty that complain about Australia Post, 99.9% of the time, they deliver the mail.

No one forced you to use Sendle. You made that choice yourself hoping you could save a few cents. Regardless of the spam that ebay inflicts us all with, you were not forced to do it. Yet you chose to. More than once by the sound of it.

Yes, you will probably lose out on this sale. Chalk it up to experience. In future, do what most people do with ebay spam. Delete it. No reason to leave ebay over one bad experience. We've all made mistakes. Learn from it and move on.

If you send without tracking and the buyer claims not received, even if they have got it, you're going to lose even more. The buyer will win every single time if there is no tracking. Pleased you have decided to send with tracking after all.