  Intervalley scattering of carriers in graphene at `top' adatoms may give rise
to a hidden Kekul\'e ordering pattern in the adatom positions. This ordering is
the result of a rapid modulation in the electron-mediated interaction between
adatoms at the wavevector $K- K'$, which has been shown experimentally and
theoretically to dominate their spatial distribution. Here we show that the
adatom interaction is extremely sensitive to strain in the supporting graphene,
which leads to a characteristic spatial modulation of the Kekul\'e order as a
function of adatom distance. Our results suggest that the spatial distributions
of adatoms could provide a way to measure the type and magnitude of strain in
graphene and the associated pseudogauge field with high accuracy.
