Embedded queues and hiding

I use embedded queues heavily. I make a portal, include and hide to set up the cards I want, turn the portal into an embedded queue, switch to view mode, the end.

Then I start reviewing, day after day.

Sometimes, while reviewing, I switch to edit mode to tweak stuff, and I find that rems that should be part of the queue, now are hidden. I think they are always unscheduled rem, or rem that I have just reviewed, or something like that, and that if I just let them be, they will reappear in the queue when their time comes. However, I’d like to be sure about how that works, because it always scares me a bit,
as if they had been lost from the queue. This has been the case since I started using these – months ago – so I think it’s by design and not a bug or something that will change just by waiting, so I thought I’d better ask: how does this work?

Thanks!

So if you go to the parent of that missing rem and expand it (e.g. Ctrl + Shift + Down arrow), will it show this hidden rem? if that is the case then it is less worrisome. I have seen such behavior at other places (not in embedded queue because I don’t use them). Not sure what triggers it to go hiding. I don’t think it is a desirable behavior.

Yeah, I’m not talking about the rems disappearing or getting deleted but just getting hidden, which is quite worrisome in this context if it means that they got removed from the queue. And if it doesn’t mean that, then it’s less worrisome, but then I’d like to know how to properly control what cards will show in the queue.