It may be different whether the Trademark Office mailed it to you or the agency received it directly from the Trademark Office.

If it is mailed to you, a copy of the trademark rejection notice will be fine. Paper quoting trademarks is not needed, but envelopes are necessary. If the envelope is lost, it will be difficult.

If it is directly collected by the agency, I'm afraid it will be difficult to handle if the original is lost, because the date of receiving the document is on the original, but not necessarily on your copy. Even if it is, the Trademark Review and Adjudication Board may not recognize it.

What kind of situation do you belong to?