I don't, not just yet, but after going over everything last night, it seems that it is a relatively common occurence. Counting you, I can put my fingers on three or four people who had the exact same problem - the PHP lines missing from the conf file, but available in a backup.
I can take a stab at a possibility: that the httpd.conf file was the one from an earlier version of OS X, and that when people upgraded to the newest version of OS X, it never correctly plopped the new file in the right place. That's a long shot though - if that were the case, why the ".bak" extension on the new file? Doesn't make sense.
Either way, glad it's working for you.