Retirement Savings Lost and Found Act of 2021 This bill establishes an online Retirement Savings Lost and Found (RSLF), managed by the Pension Benefit Guaranty Corporation (PBGC), to assist individuals in locating certain employer-sponsored retirement accounts. The RSLF must provide plan participants or beneficiaries only with the ability to view contact information for the administrator of a plan that is sufficient to locate the plan. The bill sets forth additional reporting and notification requirements for retirement plans. The PBGC must take precautions to (1) safeguard the privacy and security of participants' plan information, and (2) permit plan participants to opt out of inclusion in the RSLF. The bill also revises provisions that permit mandatory distributions of the balances of small retirement accounts using a rollover into an Individual Retirement Account (IRA). The bill modifies the investment options available for the distributions and increases the maximum account balance that may be subject to such a distribution. A plan must transfer unclaimed mandatory distributions that are $1,000 or less to the RSLF, and the RSLF must pay the balance upon locating a plan participant or beneficiary.