There probably needs to be terminology that distinguishes from true Lost Media (no known copies exist anywhere, master copies are known to be destroyed, was never publicly distributed) vs. gatekept from availability typically by capitalism or rights issues/no home media releases
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Made this in 5 minutes (and likely has serious issues), but i think i got the general point across
I.e., Lost Media is known but no longer accessible. Restricted Media is known and hypothetically accessible but circumstances partially or fully impede doing so.