  There has been a recent resurgence in hydroxyl (OH) megamaser research driven
by Square Kilometre Array (SKA) precursor/pathfinder telescopes. This will
continue in the lead-up to the SKA mid-frequency array, which will greatly
expand our view of OH megamasers and their cosmic evolution over $\gtrsim80$
per cent of the age of the universe. This is expected to yield large scientific
returns as OH megamasers trace galaxy mergers, extreme star formation, high
molecular gas densities, and potentially binary/dual supermassive black hole
systems. In this paper, we predict the distortion to the OH luminosity function
that a magnification bias will inflict, and in turn, predict the distortion on
the OH megamaser number counts as a function of redshift. We identify spectral
flux density thresholds that will enable efficient lensed OH megamaser
selection in large spectral line surveys with MeerKAT and SKA. The surface
density of lensed galaxies that could be discovered in this way is a strong
function of the redshift evolution of the OH megamaser luminosity function,
with predictions as high as $\sim$1 lensed OH source per square degree at high
redshifts ($z \gtrsim 1$) for anticipated SKA spectral line survey designs.
This could enable efficient selection of some of the most highly-obscured
galaxies in the universe. This high-redshift selection efficiency, in
combination with the large survey speed of the SKA at $\lesssim$1 GHz
frequencies and the high magnifications possible with compact OH emission
regions ($\mu_{\rm OH} \gg 10$), will enable a transformational view of OH in
the universe.
