Unfortunately, there is nothing you can do until they reopen for phone calls. When that happens, please reach out to them at 800 829 1040.
Thank you for the prompt reply! Once they reopen, do you anticipate any issues with getting a check reissued?
Hopefully there won't be any issues. They should be able to verify on their end that the check was never cashed, and they can then void it on their end and re-issue a fresh one.
Anyone had any luck contacting anyone to help with the lost stimulus check?
Go here for stimulus info: https://www.irs.gov/coronavirus/economic-impact-payments
This FAQ site may answer your questions.
https://www.irs.gov/coronavirus/economic-impact-payment-information-center