Overall, I agree with Greg, basing that off the Union captured flags, many were not turned in, certainly more then 258 Union flags of all descriptions. It did not help that parts of Richmond burned and any records of recorded Union captured flags, went up in the fire. The Museum of the Confederacy will tell you, that they have no list on captured Union flags. The Union regimental histories rarely shed any light if that regiment lost a flag, marker or guidon.
I have to rely 95% of the time on Confederate reports and hundreds of flags they captured. Many times they left no descriptions of the flags or what Union regiment lost it.
The enjoyment of the unknown.
Have a good day/morning in America!
Shawn Prouty