Did people lose their seat at intermission?

I watched a movie with an intermission yesterday -- more on that in the next few days -- and it got me wondering:

If you get up to stretch your legs, go to the toilet or get a popcorn during intermission, what is the chance you get your seat back?

As far as I'm aware, assigned seating is only an invention of the last few decades in most movie houses, as part of an attempt to give you a more premium experience. It's been part of the same movement that's included serving you at your seat, both dinners and alcohol, and part of the industry-wide movement to prevent you from having to sweat it out in line to make sure you had a decent seat, by making tickets conveniently available for purchase online. Ah for the days when people did actually worry about a movie selling out (which rarely happens, contrary to my experience on Thursday night that I wrote about Friday). 

So if you had no assigned seat, how could you be sure that using the intermission as intended did not lose you your much cherished viewing angle of the movie?

I can think of a couple obvious practical ways to save a seat:

1) Leave your jacket there. That prevents all but the rudest and those least observant of societal rules from taking your seat.

2) Leave a friend behind to guard your seats, then switch places with them to allow them to do their own intermission business. 

But what if you are going to the movies by yourself, and what if it's summer and you have no jacket?

Of course, in the old days, it was unheard of to attend the theater alone. Going to the movies was a social activity or no activity at all. I have to imagine that the only people who generally went to the movies by themselves were film critics, or lonely unemployed individuals on weekday afternoons, when seats were not at a premium. 

I figured that there still must be a way not to lose your prime seat just because the movie is so long that it requires milling about in the lobby halfway through it. 

So, I googled.

And never got the right combination of keywords to actually get my question answered. Lots of think pieces about whether movies should bring back the intermission, but nothing about the practical logistics of it -- at least not that I could tell without drilling into a bunch of similar articles, which likely wouldn't be inclined to address my specific question.

However, in the Wikipedia page dedicated to the intermission, I did find out that intermissions are still common in movie palaces in India -- with Bollywood films of course, where they are frequently built in to the print, but also with western films, where they are enforced to encourage the profitable selling of concessions.  

I had longed to find some surefire way cinemas had of dealing with this issue, but my best guess is that it usually just works itself out on practical terms. Since it's unlikely that everyone would leave their seats, and because those left behind created a sense of overall guardianship of the status quo seating arrangement, you'd have to specifically target a particularly poorly guarded sections of the seats if you want to execute a seating upgrade, and then you'd have to hope that the number of people in your party matched the number of vacated seats. And even if you were willing to do this, you'd have to brace for a likely conflict with the people who returned to those seats and insisted they belonged to them -- a conflict that's even less palatable while the movie is starting up again and you're going to disturb everyone in the area.

Maybe the reason I got no answer on Google is that it's not actually a problem, and that a combination of good manners and practical efficiency means that people just take the seats they originally had and are done with.