Hey @sweetbeems, thanks for your report.
Indeed there was a huge problem with that migration. A fix is just merged, and as you said some data would have been deleted. 
I wrote that migration, I’m going to admit that I hadn’t considered Post.where(type: "multiple") at all (basically, polls that allow multiple votes).
I’m looking to see if I can create a rake task or script which can help folks restore the lost poll votes from backup.