Back in mid-February ... the border collie from 'Anatomy of a Fall' -- whose real name is Messi but who goes by Snoop in the film -- made an appearance at the Oscars luncheon ... where he was a big hit with all the stars, especially with Ryan Gosling, who seemed pretty smitten with the pooch.

Nothing wrong with bringing the dog from the film to make a little cameo for a pre-Oscars powwow right??? WRONG!!!! At least that's how some felt about it behind the scenes.

According to THR, production companies (and presumably studios) that have films up for Academy Awards apparently complained about Messi's presence at the luncheon ... griping that the dog being there and being so popular was giving his film an unfair advantage.

The dog showed up when Oscar voting was still going on -- and per THR, multiple companies with their hat in the ring complained to Academy honchos about it.

Fast-forward to today -- and the newest news is that Messi will be MIA from Sunday's ceremony ... a bummer, of course. Whether that decision has anything to do with the luncheon "scandal" ... jury's out. THR reports the luncheon thing had always been planned to be a one-off for Messi -- but if his being there angered that many people, who knows!

BTW, this dog is super talented -- and some have joked that it might actually be worthy of an Oscar nod itself. If you haven't seen 'Anatomy' yet ... there's a memorable scene with the dog, where it almost overdoses on aspirin ... and it plays out looking scarily real.

As it turns out ... that's because it was, meaning the dog was actually playing dead. A BTS look at how that came to fruition surfaced this week -- and it's pretty fascinating. Smart pup!