You can submit your missing mileage request online through Marco Polo Club member's area on CX website.
The catch: the flight must be less than six months ago. So this may work for
Guy Betsy, but not for
roadsleeper. If the maximum time of six months is valid for all missing mileage requests (online or otherwise), then your mileage is probably lost.
Ticket number is requested on the online form but not required.