I have an iphone 3gs running cfw 6.1.2 tethered but It wont boot even when I use 'just boot' in redsn0w. I tried restoring cfw 6.1.2 created with sn0wbreeze which is untethered but it wont restore, now the phone is stuck in recovery mode.

I dont have the shsh for 6.1.2, how can I restore the phone please to this firmware?