I had a similar issue with wanting a BF ticket from IAH to MAD. Had found one on CO.com for 2190, but a few days later when I booked it went up to 4800. I went ahead and booked a fully Y for 2850. Called a couple days later and asked about a BF fare (from a quote from a travel agency) for 2330. CO agent (international one) said he saw it and could convert my ticket and issue a refund. On top of that he said that it would be 2230, so another 100 saved.

If in doubt, just buy a ticket or place one hold and call up to make sure. In this case the agent said that the 50 day in advance rule applies so that is why it was cheaper. Why CO.com didn't have it, I don't know. I do with there were some advanced features on CO.com for us travel savvy.

Good luck and good travels!