"I was told that they would issue a corrected 1099-R since the original 1099-R erroneously shows the excess RMD."
A corrected Form 1099-R is not normally issued under these circumstances, particularly because the funds came under your control outside of the IRA. Normally you would report as a rollover the amount returned to the IRA. (However, if the distribution was from an inherited IRA paid to you as a non-spouse beneficiary, no rollover is permitted.) For the financial institution to issue a corrected Form 1099-R they would essentially be falsely claiming to the IRS that the funds never came under your control.
