I should have added a question mark - I am typing on a phone with non-dexterous fingers.
Fuel-air bomb?
Was big enough physically like the MOAB, but wrong sort of explosion - looked like an HE blast rather than the huge spreading fireball - also did not know Russia had those, but it would figure.
Maybe it was a deep penetrater of some sort. was too fast to get much of a look and now I don’t remember where I saw it - doncha just hate brain cell loss?