  In recent years, dust masses of a few tenths of a solar mass have been found
in the expanding ejecta of a number of core-collapse supernovae. How dust forms
in such quantities remains poorly understood; theories of dust formation
predict lower total masses and much faster formation rates than observations
imply. One suggestion to reconcile observations and theory was made by Dwek et
al. (2019), who proposed that the dust forms very rapidly, and because of its
optical depth, is not initially observationally detectable, only being
gradually revealed as the ejecta expand. Observational dust masses at early
times would then only be lower limits. Using a large grid of radiative transfer
models covering dust masses from 10$^{-4}$ to 1M$_\odot$ to calculate both the
spectral energy distribution and the emission line profiles from clumpy dust
shells, we show that this cannot be the case. Some clump distributions allow
dust masses of $\sim$0.01 M$_\odot$ to be concealed in clumps and still predict
an SED consistent with the observations. However, these geometries predict
emission line profiles which are inconsistent with the observations. Similarly,
clump geometries which reproduce the observed emission line profiles with dust
masses >0.01 M$_\odot$ do not reproduce the SED. However, models with
$\sim$10$^{-3}$ M$_\odot$ of amorphous carbon can reproduce both the SED and
the emission line profiles. We conclude that no large masses of dust can be
hidden from view in the ejecta of SN 1987A at early epochs, and that the
majority of dust must thus have formed at epochs >1000 days.
