  We study the effect of a non-trivial vacuum prescription on warm inflation
observables, namely the power spectrum of the comoving curvature perturbation.
Non-trivial choice of vacuum, can provide information about trans-Planckian
physics. Traditionally, the initial condition for inflation is chosen to be the
usual Bunch-Davies vacuum. Another more reasonable choice of vacuum is the
so-called $\alpha$-vacua. Because the duration of inflation is not infinite, as
it is assumed in the Bunch-Davies case, imposing the initial condition at
infinite past is not sensible and one must utilize another vacuum prescription.
In this paper, working in the slow-roll regime during warm inflation, the
initial condition for inflaton fluctuations is imposed at finite past, i.e. the
$\alpha$-vacua. We show that this non-trivial vacuum prescription results in
oscillatory correction to the comoving curvature power spectrum, which is scale
dependent both in amplitude and frequency. Having obtained this scale dependent
power spectrum, we consider its late time footprints and compare our results
with observational data and other proposed models for the comoving curvature
power spectrum.
