I fermented 12 gallons in a Sankey keg. Fermentation went fine as well as diacital rest for two days. After two days of cold crashing all of the sanitized solution that was in the blow off bucket is gone, the solution was a starsan mix. Is it salvageable?
I have noticed with any airlock, some of the solution in the air lock can go into the fermenter. Most of the time, the pressure inside the fermeter is greater, so air escapes. However, when temperature drops, pressure decreases, which causes the liquid in the airlock to be sucked into the fermenter.
In the future, it's probably best to switch out from a blow off tube to an airlock after primary fermentation has slowed, to limit the blow back, especially if you are going to cold crash.
As Denny said, StarSan, at least when diluted per instructions, won't hurt you to drink. If you've ever drank any (by accident, or doing a mouth siphon or out of curiosity), you'll have an idea of the taste. One part in twelve sounds like a high concentration, but whether or not you can taste it will depend on the flavors in the beer.
I once added about a pint of StarSan solution to my mash in a 5 gallon pale ale, attempting to bring the mash temp down a bit. I had inadvertently grabbed it from the wrong bucket and didn't realize it until much later. That beer later scored a 34 in a BJCP competition (which is pretty good for me), but it had a lot of hops (pale ale).