Drain wrote:The pet would move to get LoS, then cast. Sacrifice however, I can't remember if it uses a LoS.
I remember this being the case during TBC, as I have never played vanilla retail myself I do not know if this was the case back in vanilla. I did however find a video of what looks like a warlock sacrificing his pet while its out of LoS. The video was posted on november 21, 2006. Which should indicate its either during or before patch 1.12.2. You cant clearly see if the pet is really out of LoS though, but its the only thing I could find.
https://www.youtube.com/watch?v=_zqPR59cduw
(around 1:20 he sacrifices his VW, btw turn off the music

Drain wrote:If you used a Soulstone, in BGs or not, no pet came back with it.
I tried looking more into this but I couldnt find anything in the vanilla patchnotes. I will look into some oldschool warlock videos to see if this was actually the case. The reason why I reported it is because I remember it exactly how you explained. But again, that was during TBC.