If it was an IRA then the IRA custodian was required by law to send the 1099-R to you no later than Jan 31, 2018. There is nothing on a 1099-R from an IRA that indicates to the IRS where the money went or if it was a rollover.
If you failed to report it as a rollover on your tax return then the IRS will assume that you took the money and tax you on it.
457 plans do not report to the IRS the receipt of rollover money - it is up to you to report it.
Call the IRS number on the letter you received and explain the situation. They might only need you to send them a copy of the 457 plan statement showing the receipt of the money.
**Disclaimer: This post is for discussion purposes only and is NOT tax advice. The author takes no responsibility for the accuracy of any information in this post.**
