A personal guaranty is reviewed as a contract. You should review the guaranty with an attorney to see if there is any language that will terminate the guaranty upon assignment.
I agree with the previous answers and the language of the note could have made it assignable or excluded assignability. If the note was a payable to order or to bearer RCW 62A. 3-109 & 203 may give you some guidance but there are other factors that will be important.
Take all the documents in question to a lawyer for a consultation.
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