Yay I've found a place for this thought!!

I think Godric's sword has to be a horcrux because I can't understand why else Voldy visited Dumby to ask for DADA teaching job again, except that it was an excuse to get to the sword. Voldy would love the idea that he did it under Dumby's nose and that Dumby would protect part of Voldy's soul. The only problem with this theory is that we don't know how horcruxes are made. If it's just a matter of a bit of surrepticous wand waving and a couple of mumbled words, my theory works

my theory is strengthened by the fact that the reason Dumby came up with for the visit- Voldy really did want to come back to Hoggers 'cause he wanted to snoop- is.. well, dumb