I had somewhat similar problems trying to boot from an SSD after restoring the disk image (in my instance, FreeNAS-9.2.0-RELEASE-x64.img.xz) directly to the SSD. Since my NAS box had no optical disk device, I first tried using Tiny Core Linux, booted via a USB stick, to restore the FreeNAS disk image to the SSD using the same method as the original poster. This resulted in the pre-boot loader being displayed ("F1 FreeBSD", etc) but it failed to locate the BTX loader. Next I tried booting from a FreeBSD 9.2 USB stick (FreeBSD-9.2-RELEASE-amd64-memstick.img), entering "live" mode, and then doing the "dd" restore of the FreeNAS disk image to the SSD. This proceeded further, locating the BTX loader, however the end result was an endless stream of "#" characters being displayed on the console.
What ended up working for me was to "dd" restore the FreeNAS disk image to a USB stick, booting from said stick, entering a shell, and then copying the USB stick contents to the SSD, ie:
dd if=/dev/da1 of=/dev/ada0 bs=64k conv=sync
where "/dev/da1" was the USB stick and "/dev/ada0" was the SSD.