The error in the sentence is in the tense of the verb "have put." The correct correction is:
Sanya exclaims, "Look! My keys are in the refrigerator. I must have absentmindedly put them here while putting away the groceries."
Explanation: The correction changes "will have put" to "must have put" to indicate that Sanya believes she put the keys in the refrigerator in the past (past action), which is why she's surprised to find them there now. "Will have put" suggests a future action, which doesn't fit the context. "Must have put" implies a past action that was likely unintentional or absentminded.