I'm not sure we're on the same page here. If you have compiled the kernel, then you would have known where you compiled it from (the location of the source code)?? :\
Anyway, back as pixellany is saying, the executable for kernel file, is typically within the /boot folder. There you should find an ELF file like bzImage.. or vmlinuz...
Typically, the source code for kernels should be placed in /usr/src/kernels. But as you said, if it's not there, then it's somewhere else. If you compiled it, makes more sense that you know where you compiled it from.