Dear Ms. Ellison,
Thank you for posting your request on History Hub!
We searched National Archives Catalog and located the Compiled Service Records of Soldiers Who Served in the American Army During the Revolutionary War in the War Department Collection of Revolutionary War Records (Record Group 93) that includes 25 files for the name John Murphy. However, all the Virginia records we located were for members of the Virginia Line within the Continental Army, not the Virginia Militia, and none of them were for ensigns. We could not locate a file for John Murphy in a North Carolina unit.
Most of the records of the American Army from the Revolutionary War era that were in the custody of the War Department were destroyed by fire in 1800 or in 1814. The War Department's Collection of Revolutionary War Records was begun in 1873 by means of purchase, gifts, or transfers from other agencies. The compilation of military service records was begun in 1894, under the direction of the War Department's Record and Pension Office. Information about individual soldiers was meticulously copied onto cards as a means of consolidating information about individuals, as well as preserving the original source documents, including muster rolls, pay rolls, returns, and other records. However, if the original records did not survive until the 1890s intact or were overlooked when compiling the records, there may be soldiers that served in the war but who were omitted from these records.
In particular, many militia units were less likely to be included in these records as their records were maintained at the state and sometimes even county level rather than by the federal government. The Library of Virginia and the State Archives of North Carolina may have records pertaining to the militia units of their respective states. We located the listing for John Murphy in the publication Virginia Militia in the Revolutionary War on page 209.
We hope this information is helpful. Best of luck with your research!