Retirement Savings Lost and Found Act of 201 8 This bill requires the Department of the Treasury and the Social Security Administration (SSA) to create an online Retirement Savings Lost and Found (RSLF) 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 amends the Internal Revenue Code (IRC) to set forth additional reporting and notification requirements for retirement plans. Treasury and the SSA 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 amends the Employee Retirement Income Security Act of 1974 (ERISA) and the IRC to revise 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 or to an IRA established by Treasury. The RSLF must invest funds received in Treasury securities and distribute the balance upon receiving an application from a plan participant or beneficiary.