I have so far encountered the following creatures with See Invisibility potions.
Whilst stargazers may have started giving out tiny hand bags to their animals friends I would imagine this may be a bug?
It essentially makes these quests extremely hazardous as your only escape route if you get to low HP is removed.
Dire Rats
Rats
Bats
Giant Spiders
All the starter quests at the Ziggurat were effected as well as a number of the lower level quests around Mistlocke.
Did you see them drink See Invis in the log, or did they just trigger the visual effect and see you? There's been a system in place for ages where if you use Invis or Darkness, there's a random chance of any mob in the nearby area gaining See Invis or Ultravision.
Or if you take something out of a container.