This is a major snafu. It is happening to most people who get Social Security. Most of these people get their Social Security via direct deposit so the government has their bank routing information.
Should have just sent all SS recipients the $1,200 via their bank routing information with the caveat that after checking if you were over paid because you made over $75,000 the overpayment would come out of future social security checks.
The IRS did/does have a lot to do in a very short period of time with some very inflexible software systems (COBOL) but the public should have been better informed.