In French, the phrase bad trip is used to describe a bad experience as a consequence of the consumption of drugs or alcohol. Gueule de bois doesn’t imply any negative connotation over what happened the night before, and only relates to alcohol, not drugs in general.

According to the French article in Wikipedia, the title was inspired by another movie with a similar scenario, Very Bad Things

While I was on it, I looked more generally:

In France, using English expressions is so “hype”.

• 7 examples of titles “translation” remaining in english (more examples among the comments)
• 15 titres de films en anglais traduits … en anglais – topito

In Quebec, French is serious business so they always translate the title, even if it doesn’t mean anything.

• Liste de titres québécois de films – Wikipédia
• 40 titres de film en québécois – topito

So, for your concern, in French (from France), we can use the English term “bad trip” for a experience with drugs going wrong. And if this film was a “road-movie”, this title would have the two meanings.
(How did the Quebecois translate the term “bad trip”?)

I don’t think the case you describe is a translation to begin with.

When translating a work of art for a different speaking country than the author’s, yes, we would have an attempt of translation, good or bad.

Here, in the case of a commercial product, the choice of the foreign version’s title has almost nothing to do with the purpose of being faithful to the original title, author’s expressed ideas, feelings or story. We have a company trying to communicate for the same product on another public. Would they have foreseen (insightfully or mistakingly, that’s not important here) that the French public had more chance to come and see this movie with the title Mon oncle Philémon et ses dix-sept lapins nucléaires, they would have happily gone with it. I just don’t know where to begin for examples, there are too many. We could almost assume laziness on the faithful or literal translaters’ part.

So, to conclude this almost-non-answering answer, if your question is “Is gueule de bois the best translation for the English expression very bad trip?”, I would answer no. If you’re discussing whether this movie’s marketers’ choice was good or bad, the question is clearly out of bounds here… Your asking Why is that so? questions in fact the marketers’ strategy, not the French language’s rules, if I may.