See the very last section of https://www.irs.gov/newsroom/questions-and-answers-about-the-first-economic-impact-payment-topic-f-p... for Q F3

Print EIP2 at the top of the 3911 and follow the instructions given. I faxed the form for a client and they received a response from IRS within about 1 week. 

To complete the Form 3911:

• Write “EIP1” or “EIP2” on the top of the form to identify which payment you want to trace.
• Complete the form answering all refund questions as they relate to your EIP
• When completing item 7 under Section 1:
  • Check the box for “Individual” as the Type of return
  • Enter “2020” as the Tax Period
  • Do not write anything for the Date Filed
• Sign the form. If you file married filing joint, both spouses must sign the form.

You will generally receive a response 6 weeks after we receive your request for a payment trace, but there may be delays due to limited staffing. Get up-to-date status on affected IRS operations and services. Do not mail Form 3911 if you have already requested a trace by phone.

• If you mail or fax the form prior to the timeframes above, your request will not be processed until those timeframes are met.

Mail or fax the form to:

Note: Do not send anything other than a Form 3911 to the fax numbers below.