@The Real Halloween  Does it look like any of these google images for fake letters? https://tinyurl.com/wddxgmm You could do your own search based on the letter number "fake irs letter ### austin tx"
Did you e-file? or paper file?
Are you a third party designee?
Have you check the IRS "Where's my refund?" https://www.irs.gov/refunds
https://www.google.com/search?q=irs+letter+with+estonia+stamps could be of interest