This year, I received a letter from the company I worked for notifying me that they did not pass the 401k non discrimination test. As a highly-compensated employee, I received an excess refund check for the 2018 year, which I cashed no problem.
I also received one the year before for 2017, but forgot to cash the check they sent me, and I no longer have that original check. Am I still able to ask for a resend of that refund check from 2 years ago, and if so, would I contact my employer or the 401k provider (in this case, Vanguard)? And assuming I am able to still get that refund, how (if at all) does this affect my tax filing for 2017?