"Here are the facts: [1] A participant submitted a written request to their employer to raise their deferral rate. The written request was received and acknowledged by the employer (voice and email). [2] In the acknowledgement email from the employer, they told the participant to expect an email confirmation from the record-keeper. [3] At year-end, the participant realized they never did receive a confirmation from the record-keeping, and their request to raise their deferral rate was not implemented. [4] When the participant contacted the employer, the employer said the participant should have noticed that they didn't receive a confirmation from the record-keeper of their request. Consequently, the employer deems the participant responsible for the mistake, and the employer won't make the retroactive corrections. Who is responsible for the mistake? The participant or the plan sponsor?"