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Depends on what company the individuals use for their cell phones. See HERE. Most cellular companies only retain the actual message a few days. Metadata such as who sent whom and when can be saved a little longer.
The point is that the subpoena is unlikely to show the actual text message. However, various metadata such as IP, text message headers, etc, may still not have been deleted by the time the subpoena is received, and they may help corroborate the claims.
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