Glad you were able to get the manifest page.
Personally, I find it hard to imagine that he would have turned right around and gone back home but anything is possible. But then, if it is your Charles in Marquette in the 1911 Canada census he would then have had to return to Canada for June 1st (census day).
2 other scenarios come to mind...
The family had the form and filled it out before he left and thus included him on it or he was included on the form even though he had already left the country and nobody questioned it.
Anyway, food for thought.
PB