Freeze thaw cycles typically are only detrimental, ie break the cell membrane, if there is no cryopreservative. Since they were in snow, I bet they didn't warm up enough to make a difference. I've refrozen yeast after a vial was left out overnight, and it came back just fine. Worst case they may have lost some viability, but doubtful. Also, most of my yeast are not frozen solid, too much glyercine. Doesn't seem to make any difference in viability there.