Jena --
This shouldn't be a problem. In the phrase "POW of the Army of Northern Virginia", you should understand the word "of" to mean "belonging to". It may be that Sgt. Canady was with his command when General Lee agreed to surrender the Army of Northern Virginia.
I'm curious about where you got the information. You wrote, "It later said..." What is "it"?
If you don't have this man's service file, it can be ordered through the message board link at the top of this page. I'm sure you've already noticed the banner.
With those copies and the book about the regiment (see table of contents in the link below), you'll have a new world of information about Canady and his comrades. I'd be surprised if other relatives didn't serve with him in the same company!
http://www.loc.gov/catdir/toc/fy041/2003002227.html