The good news is that you were at least able to auto-retaliate, and if this were to happen to another player, they would only be one hit behind their opponent; however, getting the first hit in a stake can obviously make all of the difference. This issue is very troublesome, more so if it can be intentionally replicated.
From the video, it seems that the cause of the issue is the player standing below your opponent; when that player leaves, you are able to select the Attack option (as showcased at the end of the video).
As far as getting your items back goes, I would not be much of an authority on that topic.
Thank you for your report, Lordmax Xx.
