That's pretty scary. Both of my sons have been fed Isomil, soy based. They were breast-fed but supplemented with the Isomil. My three year old can eat peanuts. Does it say when the allergy developes?
Remember, it's only an hypothesis. And, if your toddler has no problems with peanuts by now, it should not be a problem. There are literally millions and million of kids and young adults doing fine today who were fed with soy formula. Please do not worry.