Controversial opinion: This happens a lot in 2019.
Ideally of course they should've hinted at it, but for the love of god, before you enter group sex in a hotel you could ask if everyone's practicing safe sex for your own benefit alone. in the age of prep and some ppl under the illusion they are now immune from all other STDs you need to be careful.
Going all "shame on them for doing drugs".. they are adults after all. And it doesnt look like it was open public drug taking. Would you prefer them doing meth and you don't even see it? If you're not into that sort of thing (I tried chemsex once, not a fan either) then just don't do it.
Not cool of them to make you try to do it without and good for you for leaving when you feel uncomfortable.

I don't mean to sound harsh, it's just part of navigating (gay) life.