As I use as a primary example, General Bragg reported that "Twenty-Five captured Union flags" were turned in at the battle of Chickamauga. We have found well over One-Hundred Union flags of all descriptions that were captured. At this point nearly 75% captured Union flags were never turned in. I am very positive there are even more Union flags that were captured at Chickamauga, we will never know exactly what is the "Last Flag."
My estimates on Union captured flags: All "Ball Park figures, flags not turned in and turned in."
1st Bull Run: 10-15
Williamsburg: 8-15
Seven Pines: 5-10
Gaines's Mill: 10-20
Glendale/Frayer's Farm: 5-10
Cedar Mountain: 5-10
Second Bull Run: 25-50
Harper's Ferry: 10-25
Antietam: 3-8
Fredericksburg: 5-10
Chancellorsville: 20-50
Gettysburg: 25-50
Wilderness: 15-30
Spotsylvania: 10-20
Cold Harbor: 5-10
Petersburg: 50-100
Appomatox: 3-10
Shiloh: 30-60
Perryville: 5-10
Murfreesboro: 30-75
Chickamauga: 100-130
Chattanooga: 5-15
Atlanta Campaign: 25-50
Franklin: 5-10
Nashville: 3-8 (Mostly Cavalry actions, rear guard)
Bentonville: 2-5
Oak Hills: 3-8
Pea Ridge: 3-8
Many more battles out there.
Have a good day,
Shawn Prouty