Did Goryachev et al. detect megahertz gravitational waves?

Goryachev et al. [M. Goryachev, W. M. Campbell, I. S. Heng, S. Galliou, E. N. Ivanov, and M. E. Tobar, Phys. Rev. Lett. 127, 071102 (2021)] recently announced the detection of ``two strongly significant events'' in their bulk acoustic wave high frequency gravitational wave antenna. They claim many possibilities for the cause of these events, including high-frequency megahertz gravitational waves. We demonstrate these events are not due to gravitational waves for two reasons. (i) The inferred stochastic gravitational-wave background from these events implies the gravitational-wave energy density of the Universe is Ωgw≈10⁸, approximately 10⁸ times the closure density of the Universe. (ii) The low-frequency gravitational-wave memory signal that accompanies any high-frequency gravitational-wave source visible by the current generation of high-frequency detectors would have been visible by LIGO/Virgo as a transient burst with signal-to-noise ratio 10⁶. The nondetection of such loud memory bursts throughout the operation of LIGO/Virgo rules out the gravitational-wave explanation for the high-frequency events detected by Goryachev et al. We discuss broader implications of this work for the ongoing experimental search for ultra high-frequency (MHz-GHz) gravitational waves.