Yes. If a tracker is of decent quality they'll have clearly explained rules for when a .torrent is deleted off the server because a seeder is 'never' coming back. A reasonable period is 14 days. So if a tracker still indexes a file, it's because someone in the last two weeks could have still distributed it, for example.
Most private trackers have a 'request re-seed' button that asks all downloaders of the torrents if they still have it on their hard drives.
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