Hey, I've done a bit of testing to help you out, here's what I found.
- If you get banned from a community, then it will show in the instance Modlog (link at the bottom of the page):
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There is otherwise no notification given to the user or any text to say you're banned.
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I could still search for the community and view it, but just couldn't post to it.
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There is no difference in behaviour between getting banned from a community on your home instance, or getting banned from a community on a remote instance.
I'm guessing you can still access the instance the community was on? Can you check the Modlog?