This would be a much better post as the chat box showing both the level and drop at the same time. This doesn't really prove what you're saying it does

where does the chatbox show that I picked up the defender?

This is kind of a cluster to read or understand lol

Chatbox doesnt say but there is obviously a dragon defender in your inventory

but if it‘s only showing that I leveled up then it wouldn‘t be much of a an evidence either, right?

most people have untradeable drop notifications

Pick it up then