Former manager Graham Drury released Silk in February — but Greene has opted to bring back the popular and experienced defender, whose Blue Square Bet North registration at The Jakemans Stadium was never cancelled.
The 28-year-old was preparing to serve a three-match ban at the time of his United departure — and is now suspension-free following the completion of three first team matches involving the Pilgrims.
Meanwhile, attacker Jordan Smith has joined Evo-Stik Premier Division side Grantham Town on loan.
The 24-year-old has scored once in 14 appearances to date for the Pilgrims.
Updated 10:53 - 14 Mar 2013 by Craig Singleton