I didn't find anything about that mark. I even checked Arnold's treatise (basically, thoroughly). Ignoring the mark still leaves a normal progression (C7 to F to B° following a cycle of fifths.) Obvious interpretations are, misprint, part of the next symbol, editorial interpolation,.... As mentioned in a comment, it would be good to see if this symbol is used again; if so, that may give some indication of use. I'll see if I can find the book it's to check things out.
I found the corresponding measures in an E major version (IMSLP). It's marked with a slash through the 6 on the fourth beat so I'd guess your idea that it signals to raise the note. I've seen slashes and sharp signs but not the vertical bar. (Could be a publishing house thing or editorial thing.) As it appears throughout the score, it's clearly intentional.