I haven’t ran into a situation where any of the digital copies of things I bought have been pulled. So I can’t speak to what happened with your friends. But I will say that if you have any purchased digital copies of movies, you should at least setup Movies Anywhere and link all accounts you have. It isn’t like how Steam will still allow you to download a pulled game. But it does give you copies of things on multiple sources once linked. So if you got something on Amazon, it would also be linked as “purchased” on other services like Vudu, YouTube/Play Movies, Apple, etc… It won’t apply to everything you have got but would likely cover most big name items.

It used to be marked with the old “Ultraviolet” branding, but when that was shutdown the basic underlying service was transferred to Movies Anywhere. Most of the time you can see which things would count because they have the MA logo. Not great for smaller releases and most shows won’t be part of it (atm at least). Though some shows might also show up, as I have seen things from HBO and some other ones.

All that being said. You are very much correct about “buying isn’t owning” these days. And even when there is something like MA, there are still thousands of movies and shows that will only ever get a digital “release” from torrents/P2P. Sad that some cool shit will never get a real HD re-master for Blu-ray (let alone streaming). I very much feel that studios should have at best a 10 year window to make whatever sales before the masters should be copied to public archives. If the studios won’t do it, then there are more than plenty of people out there that would do the job for the love of keeping old media preserved and accessible. Also bullshit when I try to go the “legal” route and find a show on one service in HD but only in SD on others. It is pretty infuriating to see that in some cases I can only get like season 2 of something on say Vudu for example, but season 1 is seemingly exclusive to Amazon. And one is in HD and the other is only SD.