I got blackjacked, when I was able to wake I got up and wingsweep'd.

You come to with a pounding headache.

<100%hp 100%m 100%mv 2297tnl (73.75%) 10 AM> You have 5 gold, 26 silver, and 11 copper, which is worth 5531 copper.
You have 109703 experience and need 2297 more experience to gain a rank. (73.75% progress)

<100%hp 100%m 100%mv 2297tnl (73.75%) 10 AM>
st
You wake and stand up.

<100%hp 100%m 100%mv 2297tnl (73.75%) 10 AM>
inher wingsweep
You focus intensely, and with a great exertion of strength and will create a mighty gust of wind with your wings.
Eliadan avoids the brunt of your wingsweep attack.

Eliadan was hidden at the time, both before and after. I assume this is a bug?

I would guess that Eliadan was visible at the time you tried to wingsweep, then went hidden right after.