Whenever I hold a flight without ticketing, it shows up in my reservations until I delete it, even though after 24 hours I cannot access the actual flights. It says something to the effect that: this res is no longer valid because it wasn't ticketed by midnight CST, blah, blah, blah. . .
Even though I can't access it I must manually delete it. IOW, there should be something there if you accidentally held but did not ticket. Also, when you go back through your e-mail (if it wasn't deleted) you should find either a held reservation notice or a confirmation notice.
I have never tried to book without logging on, so this might affect the way a held reservaiton is saved.
I think the choice to ticket or save comes right after you choose your flights, when you click "continue".
Of course, reservations do occasionally get "lost" from the system; if you can find your confirmation they should honor it. Was there a charge on your credit card bill for the ticket? That would also be helpful evidence when you approach CO.
Good luck.
O