Final answer:
The correct sentence is "Yo la busqué."
Step-by-step explanation:
The correct sentence that substitutes the bolded phrase is Yo la busqué.
When the direct object is a singular feminine noun, it is substituted by the pronoun la.
For example, if the sentence was "Yo busqué una pulsera para Mariana," the correct substitution would be Yo la busqué.
Learn more about Substituting direct objects