Your procedure is going to be based on your FI's processing and documentation storage policy and procedures. If one is not in the file I would hope that you can accurately reproduce the disclosure from your system.
Reg Z has nothing to do with the GFE, Reg. Z would have retention requirements for the TILs.
BTW, if you sell the loan servicing released the purchaser now takes on the responsibility of retaining the Settlement Statement for the remainder of the 5 years.
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The opinions expressed are mine and they are not to be taken as legal advice.